Reworked the UIColor extension:

[maxim-papier]

• Removed unnecessary hexString() method
• Grouped colors into two categories Main and Additional using enums.

Assets:

• Renamed colors to Asset using camelCase to use the same names in the UIColor extension to avoid entering a rawValue for each color.
• The color Green appears in the layout in Figma twice, in Main and in Additional. To avoid confusion, I renamed Green from the Additional set to lightGreen.