Highlight the current line in edit mode. So you know, if you are editing or not :)
<br>:hi CursorLine cterm=none ctermbg=52
<br>:au InsertEnter * set cul
<br>:au InsertLeave * set nocul
<br>
<br>Please notice:
<br>The change back to black needs about a second or so.
<br>The color 52 is only available when 256 colors are active (:set t_Co=256)
<br>
<br>Instead of the current line, also the whole background can be used:
<br>:au InsertEnter * hi Normal ctermbg=52
<br>:au InsertLeave * hi Normal ctermbg=black