Mismatched lights.

What is the negaive to using different lights. I know they might be different K. Would a custom white balance fix this? I have 2 of these light from this post. https://photography-on-the.net/forum/showthre​ad.php?t=132816 (main and fill or background) and a halogen light from an old video camera.(backgroud or hair) Would the results be acceptable for portraits?

I would say to try it with a custom white balance and see. it might be okay for a hair light.

The deciding factor is the bulb that the light uses. Halogen photographic bulbs are either 3200K or 3400K but I don't know what the video light is using for the bulb. Better quality lights will use a standard bulb which will have a standard color temp, but it may have a non-specced household quality bulb which could be as warm as 2600K. Actually, a warmer light for the hairlight can be very attractive. I often filter the hairlight with a slight warming gel to get that effect.