Black is fine.
Polyester and other artificially fibers make you hot, because they are not breathable like cotton or linen.
If you're worried about sweating, look for 100% linen, linen/cotton blend, or cotton wovens such as batiste, poplin or muslin. Not cotton jersey, which is a stretch knit, clings to skin and is usually thicker and warmer. Also look for looser fabrics and sleeveless or flutter sleeves.