I like the subtle, moody purple/gray that I can achieve by mixing Alizarin Crimson and Cerulean Blue.   Also, Cadmium Yellow and Cerulean Blue make a rather bright green that can be dulled a bit by adding a bit of Alizarin Crimson.  These three paintings were done with the following color palette-

Alizarin Crimson

Cerulean Blue

Cadmium Yellow

Titanium White

Shady Path  $30

Evening at Riverbank.  $30

Rustic Bridge    $30