A pink expression in the mycelium within the substrate or the fruiting bodies itself is OK, and generally a sign of a happy grow! Pink tends to express in cooler temperatures and when direct sunlight is applied to the substrates. Do not go out of your way to give most mushrooms light outside of ambient light, I would not recommend direct sunlight but I did want to mention another cause for the pinkness.
Brown can be a sign of dryness or significant over maturation of the mushroom fruiting bodies, keep humidity high for pinning, keep it above 60% for fruiting and you should be fine. Airflow can dry fruiting bodies, if your fruits feel or look dry, they are. Red/orange/rust color is a sign of windburn, windburnt fruits can recover but they will grow irregular.
Yellowing (usually starting at the middle mass of the fruiting bodies towards the top) indicates maturation, you want to harvest before this point for best results, the mushroom is close to sporulation at this point. It’s best to harvest when the teeth form distinct spines. What does this mean? When you can clearly identify teeth, they’re good to harvest. See this post for where I like to harvest.