Solutions to winter scalp with colored hair?

I have colored hair (dark brown almost black) and would like to make my color last as long as possible. However I suffer from dry, itchy, flakey scalp in the winter and everything I've tried to help it has either faded my color or done nothing at all. I typically was my hair every 3-4 days. Any longer and my hair gets disgusting and greasy, and any shorter and my scalp is too dry and even more itchy and flakey.

I'm on a budget so I would prefer something that's easy to find at a drugstore, but I'm also desperate so I'll consider looking beyond that. (I've tried diy masks and learned I'm not great at that so I would rather just buy something all ready made).