[Robert A Cook PE]

The rule of thumb I was taught over 50 years ago was colors in cold and whites in hot.

Fine. THIS “study” examined T-shirts. And, more importantly, “fiber-loss from the T-Shirts while washing many times in either hot or cold water.

Great. Washing cotton clothes in hotter water continually caused fiber loss over time. (Fibre-loss actually - this was a British study after all.)

What about “dirt loss”? Is not “removing dirt” more important than “minimizing loss of cotton micro-fibres” ? Yes. My hot-washed cotton handkerchiefs and socks do lose mass over time. And, after 4 - 5 years, they are regularly replaced.

[philman_36]

These observations provide evidence that, in a ‘real’ situation, increases in washing time and washing temperature increase dye transfer.”

Like I said, what I was taught still seems to hold true. Colored clothes in cold water.
I'll keep washing my whites in hot, along with bleach for keeping them white.