Design nit: Use only one shade of black

[satsie]

The website currently has three different shades of black:

• "Bitcoin Scholarship" is written in #12182a
• The "Apply Now" button is #000000
• The footer is #111828 (navy!!!)

Can we please update everything so it is #12182a? Please make sure this color update is made anywhere that a shade of black is used. I know some of the subheadings and regular text is written in gray. That is fine. Please leave anything that is gray alone.