When I launched HoudahSpot this morning, the program's auto-update feature told me that there was a new version available, and listed the new version's bug fixes and added features. One of the last features caught my eye, as it's one of the things about HoudahSpot that I didn't like: you can now set the field header background color via a hidden preference. Just enter this command in Terminal (after quitting HoudahSpot):

defaults write com.houdah.HoudahSpot accentColor color_to_use

Replace color_to_use with one of red, green, blue, grey, or yellow (the default). Relaunch HoudahSpot, and you'll see your newly-chosen header colors. Hopefully a future release will bring a true pref with a color wheel to set the title bar background colors, but this is a usable workaround for now.

(This isn't much of a hint for those with HoudahSpot already installed, as they'll see the same message when they update the program. However, for those downloading the latest version for the first time, this hint may be of some assistance.)