Fix color mode flashing

[TClark1011]

Currently, if the user has previously selected the dark mode color scheme when they load up the site, it starts as light mode then quickly switches to dark mode, creating a "flashing" effect. The desired behavior is for the site to appear in the correct color scheme on the first render. The rules for determining the correct color scheme are:

• If the user has no color mode preference for the site, it should render in their preferred color scheme
• If they do have a color mode preference for the site, it should render in that color mode