Update background color of the 'BUNK' button in LoginActivity, so that it is consistent with the theme colors

[Abhijit Parida]

See:

1. app/src/main/res/values/styles.xml
2. app/src/main/res/values/colors.xml

[Davide Gavio]

I'd like to work on it!

[Herman Menor, Jr.]

See:

1. app/src/main/res/values/styles.xml
2. app/src/main/res/values/colors.xml

What do we need to change here? @abhijitparida

[Talha Bin Tariq]

Change primary color or define appthemecolor in color.xml and used it for bunk button