3.1.2 How to check for non-colorfastness
Select an inconspicuous part of the garment. Place a white towel under the cloth, pound the garment about 10 times with another white towel soaked with undiluted liquid neutral detergent (for clothing).If the color of the garment is transferred to the towel, do not wash the garment.
Be particularly careful to check dark red or dark blue garments for non-colorfastness.
It is difficult to determine non-colorfastness for light colors such as yellow; for these colors, check for transfer of color after you have dried the towels.