Tol colors

Creates a palette with up to 12 colors that are easy to distinct everywhere (print, screen, B&W), for everyone (color-blindness) and pretty.

The colors created by Paul Tol at SRON are good for publication-quality figures:
https://personal.sron.nl/~pault/
- distinct for all people, including color-blind readers
- distinct from black and white
- distinct on screen and paper
- still match well together

ptc6 calls up to 6 RGB colors.
use ptc12 if more colors are needed (up to 12).

Usage:
ptc6(n) % n is the number of distinct colors
(a light gray is added at n+1)

Example:
TOLC=ptc6(5)
plot(1:10,sin(1:10),'Color', TOLC(1,:))
hold on
plot(1:10,sin((1:10)+1),'Color', TOLC(2,:))
...

To visualize each scheme of color selected, add 'check' to the function:
ptc6(3, 'check') % displays the 3 colors on a figure