Why
not just add black?
You can.. However a lot of artists feel by adding a colors opposite
on the color wheel, gives more interesting and lively darks.
You don't ever need to get a black if you use this method as
you will be able to make any black (reddish, greenish or bluish
ones) you need. A purest may say different.. to each his own.
A
tip to making the lightest tint ..
If you are wanting to make the lightest tint of a color, you
should consider starting with the White paint first and add
the smallest dot of the color..
You will be surprised how little is needed to color the white.