From what I've read...yarn dyed with Koolaid will fade if overexposed to sunlight. Other than that, it seems to hold it's colour pretty well. I can't see it being a huge problem...unless you spend a lot of time in the sunlight wearing your Koolaid dyed creations.
a lot of dyes fade when exposed to sunlight no matter what kind.. even light fast ones can change and fade.
now that being said.... I saw my friend Carole yesterday... and her handpainted hand spun koolaide colored gloves she wears them all the time in the winter... for the past 3 years..... they are as bright now as the left over ball of yarn we compaired them to
does that help? make sure you fix the color well by acid and heat