I said that I was over writing about marking the active window and changing mode line colors, but, as they say, never say never. If all you want to do is change the color of the active mode line to something that stands out more than the default slightly darker gray, all you need to do is follow Ignacio Paz Posse’s advice that I described previously.
But if you want to understand what’s really going on, Prot has new video that explores mode line colors in depth. Part of the video is about how to work with his custom themes but most of it is applicable to any—or no—theme.
The video has some really useful information such as how to get a color palette of all the themes installed on your system and how to get a palette of all available colors so you can choose whatever appeals to you. He also explains the difference between the set-face-attribute command, which I used to change my mode line color, and the related custom-set-faces command which is similar but sets colors that aren’t overridden by a change of theme. See the video for more on this and how it works.
The video is just over 34 minutes so you’ll need to set some time aside but it packs a lot of information into those 34 minutes so if you have any interest in adjusting your mode line colors, it’s a must see.