Color customization in message list

[someone]

Is there an explanation somewhere of what the color customization at the bottom of the message list settings screen or do I need to discover what they do by trial and error.

For example, what is a "group header", etc?

[Kostya Vasilyev]

Group header color is the color used by group headers -- when messages are grouped by date, etc.

It's the blue things that say "Fri, March 14" etc.