So, I have some bows & bands on next weeks cake. The color is a very pale delicate pink. I have colored the fondant 3 times. Normally, the color gets deeper with time. On 3 separate occasions, I have colored the fondant a pale pink, put it back in the airtight tub, left a day or 2, and returned to find fading. Not only does the color fade, it's as though it all pools in the bottom. The top fondant is white and gets darker at the bottom but even that is lighter than original. I mix it all back up, add a bit more pink...same thing.

I also mixed some satin ice gum paste, made bows, & set. The bow loops were perfect. Today, about a week later, they are faded. Some of them are streaky as though the color was just falling off to the bottom.

Possible causes? Helpful tips?

Purples and pinks always seem to fade. It helps if you keep them in the dark. They will probably still fade a tiny bit, but it helps a lot.
I found the brand "Sugarflair" hardly fades at all with the pinks and purples.

I bought two viles of no fade purple and no fade pink and couldn't do without them. Someone on this site suggested adding a little baking soda to help colors keep. This memory is a little fuzzy on that so maybe someone else could chime in.

That was me

Colors fade in fondant because the pH is off. You add baking soda to fix that.

Keeping stuff in the dark does not work or slow fading. Only fixing the the pH in the fondant will!

I've been testing Satin Ice lavender - for the roof of a princess castle cake. Kneeded and rolled out and overnight it's turned a shade of grey. Needless to say it's a brand new tub and I'm gutted. I'll give it a go using the baking soda and update. Great advice - fingers crossed

So - an update. I contacted the Satin Ice peops. They responded advising both the lavener and purple are prone to fading in light. They suggest 1tsp baking soda to a 500gms of fondant as a fix. There's two downsides to this 1) if you're not intending on using this quantity it's a case of using how much??? and 2) if you're wanting the fondant for eating it might taste pretty yuck! Anyway's I know I cant take the risk of finishing this cake this weekend for it to fade after a day of being out in the open so I'm going to use white with gel paste. Even more fingers and toes crossed.

I ended up mixing a bit of red fondant with white. Solved my immediate problem.