What colors make the color bone?

Photoshop

If you mean ivory, or literal bone color, you can do this in multiple ways to create a 'bone' effect:

Digital:

Using SAI or Photoshop, on the color wheel (suggested) use a really really light/pale yellow-get as close as you can to white while still showing a hint of yellow.

Traditional:

If you're using paint, mix a small bit of yellow into a lot of white.

When using pencil, just use a fleshy, pale yellow-like a vampire, or that emo kid at school's skin kinda yellow :)

These apply to most traditional forms of art...

So basically, yellow and white :)