Here's a list of elements that can be customised in the Dashboard Customize Theme are:
Body Background Color
Page Background Color
Logo Font Color
Header Banner Font Color
Header Banner Paragraph Color
Banner Background Color
Navigation Link Color
Navigation Path Selected Link Color
Navigation Hover Link Color
Content Header Font Color
Content Paragraph Font Color
Content Link Color
Content Link Hover Color
Content Link List Font Color
Content Link List Hover Font Color
Content Link List Selected Font Color
Sidebar Header Font Color
Sidebar Paragraph Font Color
Sidebar Link Color
Sidebar Link Hover Color
Sidebar Link List Font Color
Sidebar Link List Hover Font Color
Sidebar Link List Selected Font Color
Footer Header Font Color
Footer Paragraph Font Color
Footer Link Color
Footer Link Hover Color
Footer Link List Font Color
Footer Link List Hover Font Color
Footer Link List Selected Font Color
To achieve WHITE color in your text for your banner simply use the BOLD tag in the WYSIWYG editor.