ConstColours constructor Null safety

1. mc_gallery
2. const_colors
3. ConstColours
4. ConstColours constructor

ConstColours class

1. Constructors
2. ConstColours
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. noSuchMethod
8. toString
9. Operators
10. operator ==
11. Constants
12. black
13. galleryBackgroundColour
14. red
15. transparent
16. white