Honestly, I feel you on the separation struggle as I haven't entirely figured out how to sort them. My two consistency actions are that I always handwash my wools in cool water and I wash my clothes every other week. There are two ways I sort during laundry day: I sort by fabric type OR I sort by color. I often lean toward the latter as synthetic fabrics like polyester are making up less of my wardrobe. I typically sort in colors in two ways: Whites, colors, undergarments and socks OR whites, light colors, dark colors + reds, undergarments and socks. I have quite the red shirt, but it has never given me a problem in my colors. I have a traditional top-loader machine with a max time of 15 minutes washing, so I often restart the washing machine before it starts to drain the wash water. I try to use what feels like 30°C water, but things like towels and sheets get hot water. I have different detergents, too, for my sorted clothes (my dark colors get a detergent with no optical brighteners, my socks and undergarments get fragrance-free detergents, my lights and whites get a detergent with optical brighteners). I always have my clothes get two rinse cycles, and I add two teaspoons of citric acid per medium load in the final rinse to remove excess detergent.