I did not think of this first, as the idea came from a DAA Painter class forum. But I thought it was a great idea, so I'm expressing the idea as a suggestion, to incorporate into next P21 release....
Painter has many dab types that allow us to sample multiple colors from the mixer pad and use them directly with brush at hand and get great results.
However, try to duplicate the sampling later is nearly impossible. Normally if we get close that is OK and adds character to the painting.
But, if we didn't happen to save the mixer pad and remember where to take the sample....it is very difficult to even nearly duplicate later in the painting, or to come back days later to finish a painting....or worse, try to do a similar paint stroke on a new file.
BUT, all can be OK if a feature is added to be able to name and save a 'multiple color mixer pad sample' color...say to a new new kind of color library while that sample is currently active on a brush. right click outside the canvas/layer and click on "save multiple color".
We know the color sample information is stored in the program temporarily; simply have a user GUI to allow for the color sample save; and probably save the brush and its settings (those are also at hand in temp memory in program)....so maybe the saved info dialog window fills in the multiple color and brush data name and user adds some useful identifier.
Maybe the "library" name defaults to the brush name and user 'names' the color description? Maybe the mixer pad also gets saved within that library?
I'm sure there is a smart coder that could code this in a few days.
Result is a new Painter feature to make painting easier and repeatable when desired.