I feel with front loaders today (or from the past), they were/are "green" by default.

Unless you altered your machine it pretty much uses the least amount of resources (water, power to heat water), detergents, bleaches, fabric softeners etc.

Back in the top loader days, I did a load of whites and a load of colors and selected the water level appropriate for that load. My resource savings was to not do a second rinse.

The only issue I had going from top loader to front loader was dosing.

Otherwise I didn't change they way I do laundry.

I have whites, darks and reds. I don't sort by fabric type but I do seperate for drying. Fleece and throw blankets get dried seperately from clothes. Using a dryer is anti green to begin with :).

With the newer machines, there are smaller load washes available. If you wash heavier towels with light-weight t-shirts, you'll wind up with wet towels. I occasionally wash some darks and lights together if they can all take a warmer temp and they have similar dirt components. My husbands jeans and the house-cleaning rags can all be washed together, lol, since whatever solvents may still be in the rags can only help clean his jeans.