Boiling algae to determine type: red

I believe that it was Paul Kombholtz who recently said.....

>I have noticed that red algae (which normally looks dark green) turns
>bright red when exposed to hot water. Take a sample and boil it if you
>want to be sure of what you're dealing with. You can also use tap water
>as long as it gets reasonably hot.

Well, I boiled an anubias blade with a bit of red algae attached to
it for a couple of minutes. The algae was dark green both before and
after the treatment. It was about 4 mm in length and appeared similar
to what The Optimum Aquarium labels red algae on page 123, item #2.
What gives? Any comments?

My apologies to Paul if the attribution is incorrect.