The colour on our hair fades in a few different ways - from sunlight, environmental oxygen, friction, washing, and perspiration.
Shampoos labelled as colour safe tend to have a lot of gentle surfactants in them, and they increase the mildness by using lots of moisturizers and anti-irritant products. They can include anti-oxidants (like citric acid, which also helps to balance the pH, or extracts) and UV protectants in the products as well. You can reduce the friction while washing by not piling your hair on top of your hair and massaging gently instead of scrubbing the heck out of your scalp!
Shampoos containing SLS are by definition not mild, so any shampoo with mild surfactants will be fine for colour treated hair. If you want to make your own, choose a daily use conditioning shampoo even if you're washing only a few times a week. Since I always formulate with gentle surfactants and increase the mildness, you can use any of the conditioning shampoo recipes on this blog. Reduce the surfactants to between 15% to 2% for a daily use shampoo (more on this later this week).
Conditioners are almost always, by definition, safe for our colour as conditioners help reduce the friction and form a film to make our hair more lubricated. Since dyed hair is almost always considered damaged, we want to use a good conditioner filled with cationic quaternary compounds, film formers, and silicones to reduce the friction caused by combing, sleeping, and other daily life kind of things. If you find your colour is still fading more quickly than you'd like, then use a leave in conditioner to protect your hair further, and finish up with a silicone spray (90% cyclomethicone, 10% dimethicone in a spray bottle).
You can add anti-oxidants to your products in the form of 1% Vitamin E, or in the form of various extracts like green tea, rosemary, grapeseed, or chamomile (to name a few) or hydrosols.
As for UV protectors, you can add a little Parsol or other sunscreen ingredient into your conditioner, but this is a really specific process and takes a ton of work to make it a successful product, and you still won't know if it is working. You could add some oils with potential UV protection like sesame seed, avocado, or raspberry oil, but again, there's no guarantee these will work.
To summarize: There is a bit of marketing hype here as all gentle to mild shampoo products can be considered colour-safe. As for the conditioners, those with good conditioning agents, film formers, silicones, and oils will reduce the friction that can cause hair colour fading.
As usual, great question, Mich!