In my opinion the paint would not specifically matter as long as it was well-cured before adding fabrics. However, light and dust are not friendly to fabrics. I would add a curtain or something to the front of the bookcases if you are going to store fabric there. Fabric also needs to be aired out if you don't want it to smell like used thrift store does. You can alleviate this by keeping a small bar of dial soap or a Bounce fabric softener sheet on your shelves but not touching the fabrics. This also helps repel any pests.
Good luck! There are 4 bookcases in my workspace. They are white so that I can more easily see...but there are no fabrics there...just books, tools, supplies, etc. Fabrics are in drawers sorted by color and type.