Flymake colouring?

Question

I've recently updated my Emacs from 26 to 27, and now the Flymake error indicators are very hard to see - they're now in a very pale rose instead of crimson red. How can I change the colour back? I've searched the documentation and also looked at the code a little (I'm no Lisp programmer, though), but could not find it. So far, the two affected regions are the margin with the error indicators, and the status bar which also displays the buffer name, editing mode etc.

Answer 1

1. Put your cursor on (just before) a character that has the colored text, and use C-u C-x = (command what-cursor-position).

2. Near the bottom of the *Help* buffer you'll see the name of the face(s) used on that character.

3. M-x customize-face and enter then name of the face. Customize it to change the foreground or background color etc. Save your customizations.

C-h k C-x = tells us:

C-x = runs the command what-cursor-position (found in global-map), which is an interactive compiled Lisp function in simple.el.

It is bound to C-x =.

(what-cursor-position &optional DETAIL)

Print info on cursor position (on screen and within buffer).

Also describe the character after point, and give its character code in octal, decimal and hex.

For a non-ASCII multibyte character, also give its encoding in the buffer's selected coding system if the coding system encodes the character safely. If the character is encoded into one byte, that code is shown in hex. If the character is encoded into more than one byte, just "..." is shown.

In addition, with prefix argument, show details about that character in *Help* buffer. See also the command describe-char.

You later commented that the chars are displayed in an area (e.g. margin) where you can't put the cursor. In that case, you can try visually matching their face against the faces you see in M-x list-faces-display. That's usually sufficient.

Otherwise, look in the flymake Lisp code to see what faces it defines and what their default appearances are.