Check with Auto Zone. They sell red shock boots that make perfect fork boots and can order different colors. The part number is SB112-x (the x being a color code, r for red, b for blue etc). I don't know if they have white but it's worth a shot to ask them.
If you can't find them, you might try some of the stuff I used on my Tri-Z seat. It's a penetrating spray dye. Check the "Vinyl paint?" thread.