I'd like to be able to specify a 'start' color(s)
This would be great if I could start with the colors that I already have and then build the swatch
Channing Hinton commented
I agree with this one. I use this website all the time and simply edit the url to start with colors I want. However, its simple coding to allow for some sort of simplistic interface to allow dragging the colors around, clicking to edit the swatches themselves, turning the swatch labels on and off, adding or deleting swatches and defining multiple swatch groups. Honestly I don't think anyone even pays attention to this site.
Andrew Varnerin commented
You can. Look at the web address, replace the *'s between the commas with your desired color hexcodes. (leave out the hash).