Individual colors for oil pastels are available in Sakura Cray-Pas
Expressionist series (Sax has them - other companies may, too). Only
twelve colors available individually (in boxes of twelve).
For advanced students, you might consider Van Gogh Oil Pastels (about
twice the price). There are 48 colors available.... Dick Blick has
these (and may have the Sakura as well). I found these by doing a
Google search - oil pastels by individual colors.
Pardon the "commercial" (smile).... Just answering a question asked by
two members. For the other one on pens - buy some samples and
experiment. I left all of my Gel Pens at school... Wish I had taken