Great but hard is that Tyranids can be any color...
Does the hive mind adapt the colors to blend in with the planet- green, black, or red.
Does it go with bright colors to scare and terrify the opposition?
Does it go with more neutral colors.
Could even have different Tyranid bio-organisms of different colors in the same army.
For my Tyranids I have a green and yellow color and a purple and yellow color.
For the purple bugs they are not painted at all- literally.
I primed them white and used GW washes to color them- sepia for the base, yellow wash for the fangs, teeth, etc. purple for the armor plates, and red wash for the eyes.