This is a simple plugin that highlights operator characters for every language. I want characters like +,-,/,*,.,:,= etc. highlighted in every programming language I write, so I wrote this simple script.

The default color for operator highlighting is cyan, but this can be changed by setting a different value to the g:ophigh_color variable for terminal and g:ophigh_color_gui variable for gui. For instance, adding let g:ophigh_color = 226 and let g:ophigh_color_gui = "#F6FF00" to your vimrc will highlight all operators with a bright yellow color.

You can also configure the plugin to ignore certain filetypes and thus not highlight operators in them. This is done by adding a new key to the g:ophigh_filetypes_to_ignore dictionary (with whatever value you want, only the key needs to be present). For example: g:ophigh_filetypes_to_ignore.markdown = 1.

If you add that to your vimrc, then markdown files will be ignored. NOTE: the key needs to be the filetype, not the extension! You can get the filetype of the current file in Vim with :set filetype?.