Bookmap indicator for ninjatrader

Hi everyone,

i am working on a bookmap indicator for ninjatrader.
The indicator works fine, but i have a problem with the visual part. Not the coding, but the logic.

Did anyone write a bookmap indicator before? My question is,how do i apply different colors to different order sizes? Is there a way to change the shade of a color from the code?
Also, on different instruments, there are different pending order sizes. How do you manage that one visual fits all instruments?

Thanks for any advices