This is a TextMate theme based on the excellent Monokai theme but tweaked to suit my sensibilities. The name of the theme came from the vibrant colours of the Tetra Neon fish that my parents kept in our tropical fish tank when I was a kid.
To install, simply download the zip and either double-click on the Charcoal Neon Tetra.tmtheme file or copy it manually to the ~/Library/Application Support/TextMate/Themes folder on your Mac.
Once that's done, restart TextMate and select the new theme on the Fonts & Colours tab of the Preferences window.