Lois Lane's Violet Eyes

Usually canon immigrants are big things like characters and events. But sometimes they're details so tiny, most people don't even realize they're there. This is an example of the latter. 

In Superman: The Animated Series (1996), Lois Lane had violet eyes to match her suit.

This had never been the case in comics before. When Lois debuted in Action Comics #1 (1938), eyes weren't given that level of definition at all...

...and once they were, she was depicted with blue eyes. 

After the animated series, however, she started appearing with violet eyes in the comics. In cases like this it's hard to determine the absolute first time it happened, but here's a smattering of examples released over fifteen years or so (the final one being a variant cover for Superman #13, July 2019).

I also can't guarantee her eyes are ALWAYS violet. Coloring is a tricky beast and there are often inconsistencies even when the colors of an object are set in stone.