finding percentage of colours

[stevem2004]

Hi,
If I know the RGB or hex code of a particular colour e.g. R252 G208 B22, does anybody know of a way to find out whay 50% of this colour would be?

TIA
Steve

[Jona]

What do you mean by percentage?

[Ben Rogers]

Are you trying to find a lighter version of the color, like gray is a lighter black? (bad example. but just go with it)

[stevem2004]

omega, yes that's what I mean, for instance if I like blue #003893, then 50% blue is #809CC9, 10% is #E6ECF5, and yes I know these are not web safe colours.

If I know the 100% ie. #EF2B2F which is a red, how can I find what the 50% would be?