Calculating a lighter shade from a passed color

Hi everyone! This place is great and the website is a big help.

I’m trying to write a function for the purpose of generating a gradient fill from only one passed color. How can you take a passed color (0x0066cc, a blue, for example) and calculate a much lighter (almost white) shade of blue from it?

Any help would be much appreciated! Thanks again for all the previous aid I’ve gotten from you guys.