How do I get oxyclean stains out of clothing?

You can’t. Bleach removes color permanently.

if you want to re-dye the fabric. You’ll have to have it all bleached, otherwise it will not re-dye evenly.

Ladies’ clothing can be creatively camouflaged, by making the stain or the bleached spot into a flower or character with fabric paints and or appliqués.

it may be possible to color in the white area with a sharpie pen.

You can’t, but if it’s just a little you could get a bleach pen and make a design out of it. If it’s big try tie dyeing it with rubber bands in strategic areas and rewash with the oxiclean.

How odd. I have never seen oxyclean remove color as it isn't a true bleach. Have you rewashed the swearshirt?