If you find something for this, I'm also interested.
The PasteColor I made does this. Currently supports hex color as input (e.g. #0099FF) and pastes the corresponding rgb values to the color picker. It could be easily modified to accept rgb as input (0,153,255).
The copy functionality would also be easy to add.
In this demo the clipboard has "#0099FF", then I moved the cursor to the "Red" input field and hit a hotkey (ctrl+shift+P), that launched PasteColor (I made a regular Windows shortcut and set this hotkey). PasteColor then converts the hex value to rgb and pastes in the fields (sends Red-TAB-Green-TAB-Blue just like ArsClip).
So the functionality is practically ready but if I could make a panel that is visible each time the color picker pops up, that would simplify its usage (would be more user-friendly).