We have all been there, you just finish knitting a project and throw it in the water to block it and the colour starts bleeding. This can mean many different things and there are several ways to keep the colour in your yarn!
You might be able to predict the first piece of advice I am going to give you… yup, that’s right. Make a swatch and wash it! This is especially important if you are doing something like colour work. If you are knitting with red and white yarn, you’re going to want to be 100% sure that red yarn is colour fast.
This is the best tutorial I’ve ever seen for fixing in colour that will fade. Whenever I am trying a new yarn, even sock yarn, I wash a swatch to see if it will fade, or bleed; then, if I need to, I can fix the dye in with citric acid and heat. As you can see, this works with finished objects or un-knit yarn alike. It’s one of the most versatile techniques I’ve come across.
What to do if this is something that is just continually bleeding colour? Like when you buy new dark blue jeans. The colour comes off of those things forever! I’ve heard that washing them with vinegar helps but it seems to me that is just an excess of dye used to get that dark colour and the indigo keeps coming off. If this is the case, I suggest repeatedly washing your garment. I had a commercially dyed yarn that was a burgundy colour, which bled quite a bit when I blocked it and any subsequent washes. After the third wash the colour stopped coming out of the sweater, but the colour never faded, it just released a bit of the extra dye.
Fading and bleeding are usually the only two problems I have with yarn and colour-fastness. They’re generally either solved with repeated washing or a citric acid soak. The yarns most at risk for this kind of thing are dark and really saturated colour. If they’re not done carefully or correctly there could be issues.