So here it is. A massively improved color picker that you can either load explicitly as the spectrum color helper, or (with reservations), use to override the existing color helper in concrete5.6+.
Please note, this is a developer level addon. To use it you will need to either:
Doing either may have fatal side effects that require development expertise to diagnose and fix. Please read the documentation. You have been warned!
I have started a list of addons that detect and use this color picker where it is installed. Developers, please add any addons you adapt to use spectrum (ie. not just overrides) to this list.
See more addons by JohntheFish