In a previous question I asked about a dragon antagonist I am planning. I originally intended this to be a chromatic dragon because I believed they are always evil, but an answer to that question got me thinking.
In the Monster Manual it states that all chromatic dragons are driven by greed and selfishness and are feared by all people.
Likewise, all metallic dragons are good.
However, are there any examples in the lore of either of these being switched? I imagine it would be more likely that a metallic dragon becomes evil than a chromatic dragon becomes good, but are there any outliers at all?
I am willing to accept any examples from any of the editions of D&D or the broader fiction written around the setting.