Is a true pure-CSS XOR blend mode possible in 2025?

As an old assembly-language guy, I think about the math in blend modes.
And I was looking at today's CSS Battle Daily and thought it would be really easy and clever if I could toggle between foreground/background colors, by using the XOR of the two values.
But mix-blend "exclusion" isn't really XOR and "difference" only works in one direction. It's not reversible like XOR.

Just something I ponder over about once a year. 😸
I thought I'd ask the hive mind if anyone has come up with a method.
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