lcd moniter does not power on and mix colour display?

thanks laure for answer........i have Fujitsu seimen lcd monitor 17". when i turn it on, it does not on and no display, when i repeat it power on to off, and again on, after three or four times repeating this procedure then it on and display,but it shows R G B, some times red colour is showing more,and some time blue and some time green. and it works all the day long, but next day it does so again.also the power supply and cable is ok.