No flags will be raised as a result in using vitamins.

The proper vitamin for "color" is B2 (Riboflavin). But it must be understood that specimen validity checks had become SOP in recent years, rendering sample color the least aspect in determining an overly-diluted urine sample. Even samples with a nice yellow color to them can still register unsatisfactory specific gravity and creatinine (the two urine constituents thats tested in determining overdilution) levels.

Therefore, when utilizing dilution techniques, the focus now is to ensure that the creatinine and S/G are within satisfactory ranges. Tips to help accomplish this are found in the Dilution "sticky" thread. When going the Dilution route, its a good idea to have some validity test strips at hand so you can keep tabs on the creatinine and S/G when diluting. These kits are inexpensive and are found online by doing a Google search for "drug adulteration test kits".