The first tab of the colorpicker can, depending on the context:
- display a selection of color combinations for the current **theme**
(when launched as a snippet option, for example, in the website builder);
or
- display a selection of **solid** colors (when lauched from the toolbar).
The commit changes the tab's name to conditionally reflect its content:
"Theme" or "Solid".
The second tab allows the user to pick a **custom** RGBA color. This commit
renames it to "Custom", replacing the inaccurate "Solid" name, now in
use for the first tab.
task-3274225
closesodoo/odoo#118852
Signed-off-by: David Monjoie (dmo) <dmo@odoo.com>