Color Boxes - can't change colors

Problem/Motivation

Cloning from #3152380: Color Boxes - can't change colors as I don't believe that was committed and closed accidentally. I can't reopen that. Anyway, I don't think that patch would help here as the problem is elsewhere.

When I use the widget "Color boxes", I can't edit the default colors. It works as long as I don't edit the default colors set by the module. But most of my colors don't work.

For example, I tried this list of colors: "#056DAB,#957000,#13224A,#774C60". Only #957000 would be displayed in the summary and on the form. There would be no error.

The problem is in how the validate method modifies the field.

      preg_match_all("/#[0-9a-fA-F]{6}/", $default_colors, $default_colors, PREG_SET_ORDER);
      foreach ($default_colors as $color) {
        if (!empty($colors)) {
          $colors .= ',';
        }
        $colors .= strtolower($color[0]);
      }

The above block of code modifies the colors to lowercase. Then, in the summary and formElement methods, we have something like:

preg_match_all("/#[0-9A-F]{6}/", $default_colors, $default_colors, PREG_SET_ORDER);

This requires that the colors be in uppercase, but that is never possible because of the validate method. The only colors that work are those which don't have A-F hex codes in them. This is why only #957000 worked in my list.

Proposed resolution

Enforce that the colors get converted to uppercase instead of lowercase as that's the expectation elsewhere in code.

Remaining tasks

* Patch