first of all, i dont understand what u mean by "run
colour"?
i tell tell you that all dyed garments has light fastness, the
matter is it it high or low. Those with bad light fastness,
exposing them in the sun, or put under spot light in close range
will fade colour very fast.
or you mean when u wash light colour garment together with dark
colour garments and it backstained. So just seperate them it will
be ok.
