Photoshop :: Colorizing A Grayscale Image Along A Spectrum

I have a grayscale image that I want to apply color to. I know how to do that by just colorizing it, but instead, I want to apply a color for the whole document. I know how to do this if I want it to be, say, blue (where black is 100 percent of my blue and 50% gray is 50% of my blue, etc.). But, what if I want a unique gradient across the image (where 100% is blue, 50% is 50% red, 10% is yellow, etc.)? How would I do that?