I'm continuing to play with a very limited palette...join me? I'm using Hansa Yellow Light, though a Cadmium would so for the yellow, Permanent Rose (or Quinacridone Rose or Quin Red) and Phthalo Blue (or similar would do). I've added Burnt Sienna and Payne's Grey for convenience colors....Indigo would work, too.
And look at all the colors possible. I've used the Burnt Sienna and Payne's Grey in the mixes, for variety. Above, yellows, reds, blues and convenience colors, reds ditto, and blues ditto! (Click on the image for a larger version.)
Even more colors are possible, if you add a bit of one of the other primary colors so you're using a triad in various strengths, as you can see below. Even a deep neutral that's very close to black. It all depends on how intense your mixtures are...
Of course the effects can be quite subtle, too...I only used the primaries in my painting of my little cat, Rags, asleep on my computer.
So give it a try, and post what you've done on our Artist's Journal Workshop Flickr group, here: http://www.flickr.com/groups/artists-journal-workshop/! Mark what you've done as primaries only, or primaries and convenience colors...and let's play!