So is a blue moon not actually blue?

I suppose to be entirely accurate, yes, a blue moon is actually blue; however, the modern day usage of "blue moon" isn't referring to a blue-colored moon.
As we use it today, the phrase "once in a blue moon" means seldom or rarely; however, the phrase does have astronomy roots. Today a "blue moon" refers to the 2nd of two full moons in a single calendar month. An even older definition says that a blue moon is the 3rd or even 4th full moon in a single season. Regardless of which historical definition you would like to use, the event is fairly rare, but it is predictable.
An actual, real blue moon is not predictable. On rare occasions, volcanic eruptions or large fires can put into the atmosphere enough particles of the right size to act like a color filter. The result is a moon that is tinged a bit blue.
https://earthsky.org/astronomy-essentials/when-is-the-next-blue-moon

https://www.spaceweather.com/glossary/bluemoonstories.html