Hah, I have NO IDEA for how long the custom colors feature has not been working... since no one reported it to me, and since it was most likely not to work for newer installations. I found today that the server where the color picker javascript code was stored, had removed that file some time in the past.
Since I did the repair, I tested it with a new install of Tampermonkey and Port Monkey in Chrome, and found it working.
If you HAD been using my scripts with Chrome, but found you had been "scroogled" by recent script policy changes in Chrome, note that I have provided new instructions for setting up scripts in Chrome, on the Port Monkey home page.
See this page for an idea of what can be done with the custom color settings.