So far you havn't received any answer, so I'll give you my opinion.
I agree with you on the colors question. Don't choose dark colors paints. Dark colors in jobsites are oppressive.
About the reflection of UV rays by gloss paints, it might be somewhat exaggerated by it makes sense. So, choose dull paints that won't reflecrt the UV rays.
Don't forget the curtains to isolate visually the welding booth from the outside. Modern curtains are made of some kind of plastic that's transparent when welding is off but get instantly dark when the arc is striken
Giovanni s. Crisi
Sao Paulo - Brazil
You need to paint in a color that is flat and non-reflective. Ideal it would be a black or a dark green I would suggest a latex paint because of the lower chance of burning paint and fumes due to strike marks, ect. I operate a school shop with 70 booths and the black painted booths reflect the least the school district painted some of the booths a flat med. dark blue and these reflect too much light. Hope this helps.
Stephen
See the AWS publication "Ultraviolet Reflectance of Paint", code ULR.