Scalp care shampoo

I went to the hair salon a few days ago and was told that my scalp was red, which has left me concerned. I have used various types of shampoo, but commercially available shampoos are generally mildly alkaline. I heard that mildly acidic shampoos are better for the scalp, so I looked up mildly acidic shampoo bars and found that they have their pros and cons.

I'm wondering which shampoo to use for my reddened scalp. Please let me know the solution for those of you with the same concern.