comments:
You can't really mix in enough soft pastels to color clay without changing the texture too much. Eventually it wouldn't hold together properly. They are great for brushing onto the surface of unbaked clay for various tinting effects, though! You can just buy blocks of Fimo Pro's recommended mixing colors (5 colors plus black and white, although you may also want translucent - Fimo Translucent has optical whiteners that can look odd with warmer colors in some lighting, so a lot of people buy a large block of Premo Translucent, which doesn't have them). Depending on how fiddly you want to get about measuring parts of clay with a scale, you can mix a huge range with good repeatability. You can get a PDF mixing chart for free, but they also sell a kit with blocks of the mixing colors minus black, which is a nice way to get started. I'm 90% sure it still comes with a printed mixing chart. If you end up going through a lot of clay, I believe all of their "True Colors" are all available in large blocks. For caning, avoid Fimo Soft (I also think it's way too soft and sticky for sculpting, personally). Cernit is reasonable for caning, Premo is less good for caning than Fimo or Cernit but still usable. For Premo, the most popular mixing primaries are Cobalt Blue Hue, Zinc Yellow Hue, and Fuchsia.