> Response codes between 500 and 599 appear flashing black on yellow to indicate a server error

Note that flashing stuff is one of the major sins of UI design, on websites as well as console applications. Even on really serious errors, flashing text is just distracting and makes the oh so important information hard to read.

I strongly recommend to remove the blinking.

Instead, you could rethink the color scheme. However, the current colors are working quite well for me, so I guess that simply removing the flashing will already do the trick.