Add color picker support in style editor

Description

All style languages support colors in HEX syntax, which is also the one giving the most flexibility.
However, in order to build such colors, we normally have to resort to external tools/applications.
Add a color picker directly in the UI instead.

Environment

None

Status

Assignee

Andrea Aime

Reporter

Andrea Aime

Triage

None

Fix versions

Affects versions

None

Components

Priority

Medium