UX improvements - Colors selections for each Item

[dinbtechit]

Hi, Great Project. However, as a UX designer and an avid user of ShareX. I feel like this project can borrow some UX ideas from shareX. Unfortunately, I am not familiar with C++ or else I would have submitted a pull request for this.

Happy to discuss!

• [x] App should remember the color chosen for each selection.

  For example: Arrow & Rectangle (as Red) and highlights (as translucent Yellow). As opposed to having to pick colors each time.

• [ ] Have default colors for each items. - Arrow, lines, circles, number sequences & Rectangles - Red - Highlight - Yellow.