Kind of like textadept now that I've played around with it, you have to a hack a colorizer (theme) to get the color scheme to Geany though. Copy and modify a theme in the themes directory under the source directory (exploded tar ball).
Presuming you named your cloned theme to be "your-new-theme". Add this to your ~/.textadept/init.lua file: ui.set_theme(not CURSES and 'your-new-theme')
Then modify the colors and type Ctrl-E for a command window in textadept and enter: reset()
Keep modifying it to your preference (hint you can choose more than the colors listed (e.g. colors.red works), once you get the color scheme you like it's not that different from Geany, and it seems a lot faster.