Fast Light Theme is a visual editor for creating and editing Aterm, FLTK and FLWM themes — the graphical trio used by minimalist distributions like Tiny Core Linux. Pick each color with a wheel, see the result instantly in the preview, and export a file ready to copy to ~/.Xdefaults.
It's a single page, no install and no server: everything is generated and saved right in your browser.
These colors affect Aterm, the terminal emulator. It's what you see when you open a console: the background, the text, and the 16 colors used by command-line programs (bash, vim, ls with colors, etc).
These colors affect FLTK-based graphical applications (the same toolkit FLWM uses): dialogs, editors, the file browser, help windows. They don't affect the terminal or the window frames.
These 4 colors affect the frame and title bar that FLWM draws around each window — the part you use to move, close, or tell which window has focus. FLWM doesn't support complex themes, only these colors.