For some time now, those of you who've studied with me will be aware, I've been advocating a palette (both in acrylic and in oil) based around the use of warm and cool variants of the basic red-yellow-blue triad. This was based on my interpretation of the book Blue and Yellow Don't Make Green by Michael Wilcox. But the cool yellow was always a problem. The closest I could seem to get in the store was lemon yellow or pale yellow.
But I have discovered Titanate Yellow, a very cool (almost greenish) yellow, and I know that it is available at Jerrysartarama.com from Golden (for acrylics) or Grumbacher (for oil paints.)
Colors are not particularly true on the web and can vary from website to website, but here are a few samples of the Titanate (or Nickle titanate) color.
Sample of Golden Acrylic's Titanate Yellow
And of Grumbacher's Nickle Titanate Yellow in Oil:
I consider this color a strong addition to your palette because it permits you to make a brillient green when paired with Phthalo Blue.