Colour Picker Badness

[LiSeag2]

When you're picking a colour, you can drag your mouse outside of the colour picker box, and the colour picker still moves, but as soon as you let go of your mouse, the colour picker menu disappears and you have to start again

[sim51]

By checking the issue, I found that users don't need to click on the submit button to change the color.
The color is changed directly on the graph, so the button is useless.

It's cool, but on the other side on heavy graph it can leads to poor performances.
Need to discuss it with @paulgirard & @jacomyal.