You can Work with the System-Color. This Color you can see in the table.
messagebox=<color:backroundcolor_aktiv>
Or you can work with RGB:
messagebox=Red =<rgb:255:0:0>, Blue=<rgb:0:0:255>
color:backgroundcolor_deaktiv  | 
Background-Color passive column  | 
color:backgroundcolor_aktiv  | 
Background-Color activ Column (with Focus)  | 
color:backgroundcolor_error  | 
Background-Color, if status=error  | 
color:backgroundcolor_empty  | 
Background-Color, if field is empty  | 
color:browse_background_ok  | 
if you work with background-color in lists then you can use the list-background-color. ok=green, info=blue, error=red  | 
color:browse_background_error  | 
|
color:browse_background_info  | 
|
color:protect_rectangle  | 
|
color:protect_color  | 
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color:column_text_underline  | 
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color:column_text_color  | 
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color:browse_detail_color  | 
Browse - Detail-Line-Color  | 
color:browse_cursor  | 
Browse - Cursor-Color  | 
color:browse_sum  | 
Browse - Sum-Line  | 
color:browse_group_color  | 
Browse - Group-Line Background-Color  | 
color:browse_grouptext_color  | 
Browse - Group-Line: Text-Color  | 
color:browse_foot_color  | 
Browse - Foot Background-Color  | 
color:browse_foottext_color  | 
Browse - Foot: Text-Color  | 
color:tabsheet_aktiv_font  | 
|
color:tabsheet_aktiv_border  | 
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color:tabsheet_aktiv_backround  | 
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color:tabsheet_passiv_font  | 
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color:tabsheet_passiv_border  | 
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color:tabsheet_passiv_backround  |