It's not different colors, it's colors and whites. Some people do whites, light colors, and dark colors, but you generally don't want to put whites in with anything that has color because the color can bleed. Red usually is the bad guy for turning whites pink, but I've turned my socks an ugly gray once when I put in a black t shirt in with them.
Keep the water on cold, don't completely dry your jeans, and don't use fabric softener on your towels and you'll be okay with 90% of your life's laundry.
@catfluff nailed it. Fabric softener contains silicone and over time it can coat your towels and make them more stiff and less absorbent. It's not the end of the world if you're adding towels to existing loads and using fabric softener. Just make sure you run a load of towels by themselves sometimes without fabric softener and they'll stay nice and fluffy.
Thanks in advance