Welcome to Librarium Online!
I'm thinking about this since a while.
The idea apeals to me to have every squad in my wych army have the highlight of their armour in a different colour. I already have one squad finished with black armour, turquoise blue en light grey highlight on the armour. Their skin has deep dark brown colours and is higlighten with bronzed and elfic flesh. Their hair (a impressive part of some models) is done in dark orange. I will add some picture as soon I can connect my cam.
I would also use the same armour highlight colour to paint the highlight on their raider.
I do fear that the unity feel to the army might suffer from this fact.
Do you have some experience with different colours in a 40k army squad? How did this work for the army look in a whole?
Any other thoughts on this?
I figured I could use the rim of the figures base to put squad colour on but is it still visible enough in CC?
As long as there is still a main color pervading through the army, your highlight/accent colors can be different. I'd say you need a couple of colors to stay the same, and then the third can be used to add a unique style to each unit. The two constant colors can include black if it is still a main part of the scheme.
I've personally never been a fan of coloring the rim of the bases unless it is with the same color as the top of the base, or at least closely related.
--•-My 40K projects-•--