One thing though, I purchased B-12 supplements at my grocery store and tried taking 10 (500mcg per tablet) and it did nothing to the color of my urine. On a whim I took 20 the next time and still no color change.

Should I look into B-2 or B-6 instead?

The proper vitamin used to "color" the urine is B2 (Riboflavin), not B12.

But keep in mind that color is the least aspect in determining an overly diluted sample. Even samples with a nice yellow color to them can still fall below the acceptable ranges for creatinine and specific gravity (the two urine constituents tested in determining an overdiluted sample).