opera:config#Colors|Skin - пишите свой цвет и наслаждайтесь после перезапуска.
Как вариант, можно добавить пункты в контекстное меню. Как-то так:
[Browser View Menu]
Submenu, M_BROWSER_VIEW_MENU_TOOLBARS, View Toolbars Menu
--------------------1
Submenu, D_PREFERENCES_COLOR_SCHEME, Color Scheme Menu,,"Mail Compose Text Color"
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Include, Browser View Common Menu
[Color Scheme Menu]
Item, 464549255 = Disable skin coloring
Item, -66645201 = Use system skin coloring
--------------------1
Item, -1616373152 = Set skin coloring, #583F28
Item, -1615957088 = Set skin coloring, #9A8454
Item, 830828255 = Set skin coloring, #479b65
Item, -1480624045 = Set skin coloring, #4E7A94
Item, -1616555806 = Set skin coloring, #283358
Item, 783034068 = Set skin coloring, #606090
Item, 1065794162 = Set skin coloring, #43354D
Item, 1074075317 = Set skin coloring, #BE324C
Item, -1480625131 = Set skin coloring, #801010
Item, Серый = Set skin coloring, #c0c0c0
Item, Чёрный = Set skin coloring, #000000
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А если нужно добавить свой пункт именно туда, где вы показали, то нужно править dialog.ini:
[Customize Toolbar Dialog]
...
Dropdown, 0, Skin_color_scheme_dropdown, 100, 300, 150, 23, Move down = Disable skin coloring,,,D_COLOR_SCHEME_NO_COLOR_S | Use system skin coloring,,,D_COLOR_SCHEME_SYSTEM_COLOR_S | Set skin coloring, #583F28,,D_COLOR_SCHEME_GOLD | Set skin coloring, #9A8454,,D_COLOR_SCHEME_SAND | Set skin coloring, #479B65,,D_COLOR_SCHEME_JUNGLE | Set skin coloring, #4E7A94,,D_COLOR_SCHEME_SEA | Set skin coloring, #283358,,D_COLOR_SCHEME_BLUE | Set skin coloring, #606090,,D_COLOR_SCHEME_INDIGO | Set skin coloring, #43354D,,D_COLOR_SCHEME_PURPLE | Set skin coloring, #BE324C,,D_COLOR_SCHEME_CRIMSON | Set skin coloring, #801010,,D_COLOR_SCHEME_RED | Set skin coloring, #c0c0c0,,Серый | Set skin coloring, #000000,,Чёрный
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