Washing

If you have a reliable cold delicate cycle on your washing machine, you are in business! I wash all my machine-washable yarns this way. Sure, they are treated with a washability finish, but if you want to keep them looking newer for longer, use the cold delicate cycle. If it makes you nervous, stick with hand-washing; they'll look newer for even longer this way.

When I've completed my project and woven in all of my ends, I place my project in a lingerie bag or pillowcase - something to protect it a little bit. I use a gentle detergent; my favorite is Soak Wash. I use the delicate wash cycle on the machine, and, if you have the option, a low spin setting (if you don't, that's ok - I didn't for years). Sometimes I will let the item soak for a bit before starting the cycle. When the machine completes its cycle, immediately and carefully remove the item from the machine, taking care to not stretch it out. I typically lay a towel down and roll the knit gently up. I use my knees to gently kneel on the roll and squeeze excess water out from it. Then carefully spread the item out onto some towels or blocking mats, and block it to shape. If I want it to dry faster, I'll put a fan on it on low.

Using dark/saturated colors alongside light/undyed colors:

If you are using a combination of very deep/saturated colors with very light colors you will want to be mindful of color-bleeding during washing/blocking. This is not a product of poor dyeing - this is simply the nature of dye chemistry. While most of the molecules of the dark/saturated dye are bonded to the fiber, some may just be "attracted" to it but not bonded. So when placed next to yarn that has many open spaces for bonding (light/undyed color), those molecules will choose the less-populated area.

Pre-washing

I do not endorse using very saturated reds or blues next to an undyed/natural color. Red and blues are very rich colors and the likelihood they will bleed onto your light color and make you unhappy is high. If this is integral to the design of your knitted piece, I recommend pre-washing your dark/saturated skein. Add about 3-4 additional figure-eight ties to your skein and then hand wash as you would wash your finished piece, until the water runs clear. This may take many rinses. Gentle squeeze out your skein and hang to dry. Again, I only recommend pre-washing for situations where a very dark/saturated color will be used next to a very light/undyed color.

Swatching

If you are concerned about bleeding, I often recommend knitting a small swatch with stripes of the colors you plan to use together and washing/blocking them as you plan to with your finished piece. It is possible that dye from the deep color will come off into the water, and this doesn't necessarily mean it will bleed. Rinse and change out the water frequently if this occurs and you will likely be OK.If the deep colors bleeds onto the light, consider pre-washing that skein and then re-swatching with your pre-washed skein.