RGB

"e.g. if you are given 0x0000FF then work a few different shades blue..."

In this case, just increase the other 2 colours equally until you get the right shade.

When you want to lighten an arbitrary colour, you need to increase the 3 colour values in proportion so that they all reach 255 at the same time.

To see it in action, look in Paint - Options-EditColors-DefineCustomColors

just reduce/increase appropriate R/G/B component. Increasing should make overall colour lighter and decreasing should make it darker.Ie:

0x0000FF
0x0000F0
0x0000E0
0x0000D0

etc

Anyone knows of an algorithm to work out a lighter shade of a given colour?

e.g. if you are given 0x0000FF then work a few different shades blue...

Cheers!