How?
See my last two posts.
Because, in my house, at least, EVERYTHING gets thrown into one load unless it absolutely MUST be washed separately. I understand that a red or a very bright garment may bleed the first time or two, but after that, I have never had an issue with color leeching out - all the excess dye is gone.
We haven't been so lucky. I've noticed a few clothing brands in particular have dyes that will transfer if not careful. I am a laundry sorter. That's the way DH and I were both taught and have always done.
Darks, lights, undies, towels, etc - it gets thrown in, I use warm water and a quality detergent, always rinse on cold. I have a large capacity, water-saving front loader, and NEVER wash on "Hot" or "Sanitary" unless someone has done something very nasty to their clothes or I am running something that absolutely MUST go separately (DH has gotten into something gunky at work, etc).
I know my situation is different because DH's clothes have to be washed separate, but how do you dry all that stuff the same way? 90% of our clothes are dried on low only and my big thick towels have to be dried on high or they would take FOREVER to dry!
I have been doing laundry this way for 20+ years and I have never had anyone complain that their clothes looked "less clean" because of it, I don't find that our clothes "don't last as long" (DD9 has hand-me-downs that originally belonged to DD18, and they are still in quite good shape.
I always wash whites/undies on hot/sanitary and separate. Growing up, both our families bleached whites / undies. My skin (and my kids) could never tolerate that. We can also only use dye free, fragrance free detergent and do not use fabric softener or dryer sheets. My eyes were opened as to how clean our laundry was (wasn't!) when we made that switch. It had always looked clean, but suddenly didn't smell clean! It's amazing what a little fragrance and some fabric softener will cover up! I specifically recall Dh's sweaty socks, baby spit up, and our kitchen towels retaining the most odor. I found smaller loads of like items and adjusting temperatures and amounts of detergent for each loads "needs" resolved those issues. DH's work clothes still stink after washing - no matter what! I really should buy some regular (fragranced) detergent for him to use, but I know he "cheats" sometimes and throws regular laundry in with his stuff.
It allows me to do about half the loads of laundry that I would have to do if everything were separated out, and I can use less water and less electricity., Just my experiences, and how *I* do fewer loads. YMMV.
I think that's great if it works for you