Example CLI command puts out dark color

[Kataglyphis]

Hi,

With the current CLI example I am not possible to generate the right-color' correctly. There might have been some changes in the code not reflected in the README.md`.

Supposed change:

# old version putting out dark background color
python -m pybadges --left-text=build --right-text=failure --right-color='#c00' --browser
# supposed change
python -m pybadges --left-text=build --right-text=failure --right-color=#c00 --browser