You do not need to cross into another Columbian. That will give you even more grief.
Please be concerned with the under color (fluff) though. I do not think that you should have any, but you will find some useful off and on.
Speaking of color, you had some questions about red bleeding through? Is that right?
I'm resisting all the advice to cross in something else. Besides the fact that I think it's too early for this project line, I don't really want to set things up so I can have a second breed going for long enough to know it well enough to create the best possible version of a third breed by combining those two, then keep all of three of them going separately ...
I do have issues with red bleeding through ... on pullets/hens. Careful inspection can find some "salmon" on some of the younger pullets, on some red feathers pop out just before POL, and after the first adult molt (18 months-ish) most of the hens grow various shades & textures of red/buff/brown on their backs where they should be white.
Both the females in my starter trio molted into buff barred backs after their first breeding season, so I worry it's terminal here. I didn't re-use either of those females. I'm acting as if it's not terminal, but how to best move forward is a bit of a head scratcher.
I have a couple of last year's breeders that seem to be coming through molt with white backs. I'm contemplating "only" breeding from them next season, though I'm doing better with type on this year's pullets.
Both my original male and the son of his I mated this year don't seem to have any buff/brown/red feathers. The son reads more "gray" than his father, and that is where I'd start looking carefully at fluff. The son's type is an improvement, though, and we've already got matings planned for him. Assuming things don't change.
I hate to admit this, but bathing the birds seems to be a good way to evaluate their fluff color.