Chromium oxide (Cr2O3) . Highly refractory. Very powerful colorant, usually requires less than 2%. Tends to volatize during firing, causing tin-bearing glazes in the kiln to blush pink.
High (5%+) Tin and small amounts of Chromium yield pinks.  Brown with Zinc. Oranges with Lead. Used to produce greens, chrome-tin pinks and (in low temperature lead glazes) yellows, reds, and oranges.