Delay an 75 ohm rgb signal
If money is not of concern, you could consider a passive delay line such as these. 

They claim that they can make delay lines with up to 30:1 delay to rise time. You are asking for about 13:1. Their standard products are only ~4.5:1 though so expect longer lead times and even higher prices. 

Perhaps there is some other way of doing this than involving a delay...