You can't fail on color. Any thing suspicious must be confirmed by lab testing and results. Validity testing usually includes specific gravity, pH, sometimes creatinine clearance, and tests for additives. Having a yellow color is not one of them. Your urine can be clear as bottled water and pass all validity testing or it can be day glow yellow and fail validity testing. Don't start adding food coloring to your urine. That is more harm than good.