very brief!
there will be a green line with a UP,1 or a 5 or a 10 or a 15 beside it. that is the manuever speed for the displayed flap setting.
for example, you're still in clean config and slowing. you will see the green UP and lower down a 1. our airline likes you to be within 10 knots of that (UP)speed before selecting flaps 1. but there is a chart on the panel that states max flap speeds which says 250 kts.
then lets say you select flaps 5. then you will see perhaps a yellow bar above and below as well as a red and black bar above and below your current speed.
looking at lower speeds first:
the amber (more correct term) ="minimum maneuver speed for current flap"
the red and black is the speed at which the stick will start shaking. stall.
at the high speeds:
when flaps are not up-bottom of amber bar indicates flap limit placard speed for next normal flap setting.(1,5,15, 30) the bar is removed when the flap lever is moved to the landing flaps selected on approach page of FMC.
the red and black for high speeds=max speed as limited by the lowest of the following: Vmo/Mmo, landing gear placard speed, flap placard speed.
the FCTM from boeing says "during flap retraction/extension, selecting the next flap setting should be initiated when reaching the maneuver speed for the existing flap position. the airplane should be accelerating when flaps are retracting to the next position. adequate manuever margin is retained at a speed 20 knots below the recommended speed for all bank angles up to 30 degrees. during flap extension, selection of the flaps to the next position should be made prior to decelerating below the recommended flap speed for the current flap setting. the manuever speed for the existing flap position is indicated by the numbered flap manuevering speed bugs."
god, i'm knackered!