Companies and Named dudes Questions!

Hey yall!

I’m very VERY new to the miniature side of 40k and imperial fists in general, and I probably have a few stupid questions about how the companies work with painting and playing the game!

So currently I’m working on 1000 points with help from my buddy’s (none of them play space marines so if yall have some advice/commentary) and currently I’m working with the space marine combat patrol/side of the ultimate starter box, assault intercessors, assault terminators, and a redemptor dreadnaught.

Later however, I would like to add Captain Lysander to the army, but from what I’ve understood is that he’s in the 1st company? I’m not the largest fan of the color scheme of 1st and would rather paint my lads as 3rd or 5th. So the big question is that is if add him to my army, does that mean I should/need to paint my guys as 1st?

Anyways thanks for listening to the ramblings of the dullest fist in the shed!