Photoshop user guide>image and color basics>choosing colors, then scroll to 'choose a color while painting'
one line says
"Note: The HUD color picker requires OpenGL(See Enable OpenGL and Optimize GPU settings)"
This is where I went to check my settings
Preferences>Performance
make sure box checked for >use Graphics Processor(restart PS if this was not checked)
under Graphics Processor settings click Advanced settings
Next
Drawing mode>choose advanced
all my 5 boxes are checked including use OpenCL, use Graphic Processor, Anti-alias Guides paths, 30 bit, use native OS GPU acceleration.
Hope you can follow this. Just a "Note" I saw. I am new to forum and do not know if links or screen shots allowed. But I do know how frustrating it is when a tool stops working the way it should.
Running OS 10.11.6, Photoshop CC(2017)