match RMI styleguide

[jdhoffa]

e.g. using https://github.com/RMI/pbtar/blob/main/src/index.css

[cjyetman]

@jdhoffa do you think this was adequately resolved by #91?

[cjyetman]

#94 fixed the Navbar color so it's blue

[jdhoffa]

Yup, can close as completed by #94