JUCE is C++ framework for multi-platform VSTi and audio application development (https://juce.com/). It comes with JUCE Projucer IDE that helps a lot with GUI part of plugin development workflow. It is great tool, but color selector GUI component annoyingly lacked ability to accept pasted hex color code. Therefore, I’ve patched color selector GUI component with “paste” button. It takes clipboard content, tries to interpret it as hexadecimal color code (with or without # prefix, in RRGGBB or AARRGGBB format) and if succeeds, sets the current color.
My JUCE Fork at GitHub
The Projucer source is in “extras” folder.