How to change theme background color, Text Color of Roku app.

I found below lines in BaseScene.xml

Theme is used to customize the appearance of all SGDEX views.
For common fields see SGDEXComponent

Than i refer the SGDEXComponent.xml and found below line
" To set global theme attributes refer to BaseScene "

I didn't find place where actual color value are added or set in both the files. Please let me know from where can i set the value of theme colors in Roku project.