You need an specific render mode to use it.
Glow or Pure Color.
With old ZHLT i remember you could make an func_wall or func_illusionary with AAATrigger texture and give it:
Render Mode: Pure Color
FX Color: R G B
And the entity will glow (as in display, it will not emit light) in that color. Also you can apply FX Amount (how visible) and Render FX (Display effect).
I have tried the same thing with VHLT but it didnt work.