Ok, so I have two colors, and I want to combine them by a certain percent ratio.

Lets say I have a red and blue, and I want the color that's 75% red and 25% blue.

I've got codes that appear to work at large ratios (like 50/50), but lets say when I try to combine 10% red and 90% white I get a blue shade.

The code I've been using to do this, broken down to make it a little simpler (so it's easier to get the idea!):
Code:
R1 = 255 * 0.1
G1 = 0 * 0.1
B1 = 0 * 0.1
R2 = 255 * 0.9
G2 = 255 * 0.9
B2 = 255 * 0.9
BackColor = RGB(R1 + R2, G1 + G2, B1 + B2)
And, once again, I get some shade of blue. Help? I'm not very good with colors!