Aug 20 21:49:38 macbookpro WindowServer[92]: Received display connect changed for display 0x4272900
Aug 20 21:49:38 macbookpro WindowServer[92]: Created shield window 0x29c9 for display 0x04272900
Aug 20 21:49:38 macbookpro WindowServer[92]: handle_will_sleep_auth_and_shield_windows: no action for lock state 1
Aug 20 21:49:38 macbookpro WindowServer[92]: Received display connect changed for display 0x3f003d
Aug 20 21:49:39 macbookpro WindowServer[92]: Display 0x04272900: GL mask 0x1; bounds (0, 0)[1440 x 900], 36 modes available
Aug 20 21:49:39 macbookpro WindowServer[92]: GLCompositor: GL renderer id 0x0102260e, GL mask 0x00000003, accelerator 0x00003c7f, unit 0, caps QEX|QGL|MIPMAP, vram 256 MB
Aug 20 21:49:39 macbookpro WindowServer[92]: Display 0x003f003d: GL mask 0x2; bounds (2464, 0)[1 x 1], 1 modes available
Aug 20 21:49:39 macbookpro WindowServer[92]: Created shield window 0x29ca for display 0x04272900
Aug 20 21:49:39 macbookpro WindowServer[92]: Created shield window 0x29cb for display 0x003f003d
Aug 20 21:49:40 macbookpro WindowServer[92]: **DMPROXY** (2) Found `/System/Library/CoreServices/DMProxy'.
Aug 20 21:49:44 macbookpro WindowServer[92]: post_notification : Time out waiting for reply from "Flux" for notification type 109 (CID 0x16603, PID 992)
Aug 20 21:49:44 macbookpro WindowServer[92]: Display 0x04272900: MappedDisplay Unit 0: Startup Mode 1440 x 900, CGSThirtytwoBitColor, Resolution 1, IOMode 0x80000000, IODepth 0x2, IOReturn 0x0
Aug 20 21:49:44 macbookpro WindowServer[92]: Display added
Aug 20 21:49:44 macbookpro WindowServer[92]: Display removed
Aug 20 21:49:44 macbookpro WindowServer[92]: Display 0x04272900: GL mask 0x1; bounds (0, 0)[1440 x 900], 36 modes available
Aug 20 21:49:44 macbookpro WindowServer[92]: GLCompositor: GL renderer id 0x0102260e, GL mask 0x00000003, accelerator 0x00003c7f, unit 0, caps QEX|QGL|MIPMAP, vram 256 MB
Aug 20 21:49:44 macbookpro WindowServer[92]: Display 0x003f003d: GL mask 0x2; bounds (2464, 0)[1 x 1], 1 modes available
Aug 20 21:49:44 macbookpro WindowServer[92]: Display 0x04272900: MappedDisplay Unit 0; ColorProfile { 3, "Color LCD"}; TransferTable (256, 3)
Aug 20 21:49:45 --- last message repeated 1 time ---
Aug 20 21:49:46 macbookpro WindowServer[92]: **DMPROXY** (2) Found `/System/Library/CoreServices/DMProxy'.
Aug 20 21:49:46 macbookpro WindowServer[92]: Display 0x04272900: MappedDisplay Unit 0; ColorProfile { 3, "Color LCD"}; TransferTable (256, 3)
Aug 20 21:49:48 --- last message repeated 1 time ---
Aug 20 21:50:51 macbookpro WindowServer[92]: Received display connect changed for display 0x4272900
Aug 20 21:50:51 macbookpro WindowServer[92]: Created shield window 0x2a18 for display 0x04272900
Aug 20 21:50:51 macbookpro WindowServer[92]: handle_will_sleep_auth_and_shield_windows: no action for lock state 1
Aug 20 21:50:51 macbookpro WindowServer[92]: Received display connect changed for display 0x3f003d
Aug 20 21:50:51 macbookpro WindowServer[92]: Created shield window 0x2a19 for display 0x19c6b0c1
Aug 20 21:50:51 macbookpro WindowServer[92]: handle_will_sleep_auth_and_shield_windows: no action for lock state 1
Aug 20 21:50:52 macbookpro WindowServer[92]: Display 0x19c6b0c1: GL mask 0x2; bounds (0, 0)[1920 x 1080], 48 modes available
Aug 20 21:50:52 macbookpro WindowServer[92]: Display 0x04272900: GL mask 0x1; bounds (-1440, 0)[1440 x 900], 36 modes available
Aug 20 21:50:52 macbookpro WindowServer[92]: GLCompositor: GL renderer id 0x0102260e, GL mask 0x00000003, accelerator 0x00003c7f, unit 0, caps QEX|QGL|MIPMAP, vram 256 MB
Aug 20 21:50:52 macbookpro WindowServer[92]: Created shield window 0x2a1a for display 0x19c6b0c1
Aug 20 21:50:52 macbookpro WindowServer[92]: Created shield window 0x2a1b for display 0x04272900
Aug 20 21:50:52 macbookpro WindowServer[92]: Display 0x19c6b0c1: MappedDisplay Unit 1: Startup Mode 1920 x 1080, CGSThirtytwoBitColor, Resolution 1, IOMode 0x80001000, IODepth 0x2, IOReturn 0x0
Aug 20 21:50:52 macbookpro WindowServer[92]: Display 0x04272900: MappedDisplay Unit 0: Startup Mode 1440 x 900, CGSThirtytwoBitColor, Resolution 1, IOMode 0x80001000, IODepth 0x2, IOReturn 0x0
Aug 20 21:50:52 macbookpro WindowServer[92]: Display added
Aug 20 21:50:52 macbookpro WindowServer[92]: Display removed
Aug 20 21:50:52 macbookpro WindowServer[92]: Display 0x19c6b0c1: GL mask 0x2; bounds (0, 0)[1920 x 1080], 48 modes available
Aug 20 21:50:52 macbookpro WindowServer[92]: GLCompositor: GL renderer id 0x0102260e, GL mask 0x00000003, accelerator 0x00003c7f, unit 0, caps QEX|QGL|MIPMAP, vram 256 MB
Aug 20 21:50:52 macbookpro WindowServer[92]: Display 0x04272900: GL mask 0x1; bounds (-1440, 369)[1440 x 900], 36 modes available
Aug 20 21:50:52 macbookpro WindowServer[92]: GLCompositor: GL renderer id 0x0102260e, GL mask 0x00000003, accelerator 0x00003c7f, unit 0, caps QEX|QGL|MIPMAP, vram 256 MB
Aug 20 21:50:53 macbookpro WindowServer[92]: **DMPROXY** (2) Found `/System/Library/CoreServices/DMProxy'.
Aug 20 21:50:55 --- last message repeated 3 times ---
Aug 20 21:50:55 macbookpro WindowServer[92]: Display 0x19c6b0c1: MappedDisplay Unit 1; ColorProfile { 4, "HF237"}; TransferFormula (1.000000, 1.000000, 1.000000)
Aug 20 21:50:55 --- last message repeated 1 time ---
Aug 20 21:50:55 macbookpro WindowServer[92]: Display 0x04272900: MappedDisplay Unit 0; ColorProfile { 3, "Color LCD"}; TransferTable (256, 3)
Aug 20 21:50:55 --- last message repeated 1 time ---
Aug 20 21:50:55 macbookpro WindowServer[92]: Display 0x19c6b0c1: MappedDisplay Unit 1; ColorProfile { 4, "HF237"}; TransferFormula (1.000000, 1.000000, 1.000000)
Aug 20 21:50:55 --- last message repeated 1 time ---
Aug 20 21:50:55 macbookpro WindowServer[92]: Display 0x04272900: MappedDisplay Unit 0; ColorProfile { 3, "Color LCD"}; TransferTable (256, 3)
Aug 20 21:50:55 macbookpro WindowServer[92]: Display 0x19c6b0c1: MappedDisplay Unit 1; ColorProfile { 4, "HF237"}; TransferFormula (1.000000, 1.000000, 1.000000)
Aug 20 21:50:55 macbookpro WindowServer[92]: Display 0x04272900: MappedDisplay Unit 0; ColorProfile { 3, "Color LCD"}; TransferTable (256, 3)
Aug 20 21:50:55 macbookpro WindowServer[92]: Display 0x19c6b0c1: MappedDisplay Unit 1; ColorProfile { 4, "HF237"}; TransferFormula (1.000000, 1.000000, 1.000000)
Aug 20 21:50:55 macbookpro WindowServer[92]: Display 0x04272900: MappedDisplay Unit 0; ColorProfile { 3, "Color LCD"}; TransferTable (256, 3)
Aug 20 21:50:55 macbookpro WindowServer[92]: Display 0x19c6b0c1: MappedDisplay Unit 1; ColorProfile { 4, "HF237"}; TransferFormula (1.000000, 1.000000, 1.000000)
Aug 20 21:50:55 macbookpro WindowServer[92]: Display 0x04272900: MappedDisplay Unit 0; ColorProfile { 3, "Color LCD"}; TransferTable (256, 3)
Aug 20 21:50:55 --- last message repeated 1 time ---
Aug 20 21:50:55 macbookpro WindowServer[92]: Display 0x19c6b0c1: MappedDisplay Unit 1; ColorProfile { 4, "HF237"}; TransferFormula (1.000000, 1.000000, 1.000000)
Aug 20 21:50:55 macbookpro WindowServer[92]: Display 0x04272900: MappedDisplay Unit 0; ColorProfile { 3, "Color LCD"}; TransferTable (256, 3)
Aug 20 21:51:17 macbookpro WindowServer[92]: Received display connect changed for display 0x4272900
Aug 20 21:51:17 macbookpro WindowServer[92]: Created shield window 0x2a47 for display 0x04272900
Aug 20 21:51:17 macbookpro WindowServer[92]: handle_will_sleep_auth_and_shield_windows: no action for lock state 1
Aug 20 21:51:17 macbookpro WindowServer[92]: Received display connect changed for display 0x19c6b0c1
Aug 20 21:51:17 macbookpro Flux[992]: CGSGetSizeOfDisplayTransfer: Invalid display 0x19c6b0c1
Aug 20 21:51:17 macbookpro Google Chrome[1011]: CGSGetCurrentDisplayMode: Invalid display 0x19c6b0c1
Aug 20 21:51:17 --- last message repeated 1 time ---
Aug 20 21:51:17 macbookpro Terminal[313]: CGSGetCurrentDisplayMode: Invalid display 0x19c6b0c1
Aug 20 21:51:17 --- last message repeated 1 time ---
Aug 20 21:51:17 macbookpro Flux[992]: CGSGetSizeOfDisplayTransfer: Invalid display 0x19c6b0c1
... Lots of 'display added', 'display removed' messages; oddly, the external monitor (HF237) was not identified until about 3 minutes later (but still came as invalid).
Anyway, unplugging and plugging the display back in still seems to be the best solution
2014 Update: after updating to OS X 10.8 (Mountain Lion) this has rarely happened. Occasionally the external doesn't properly reconnect after display wakeup or resume from standby, but not the endless looping with screen flashing blue. Unplug/plug back in always seems to fix it, it's just required a lot less frequently.