Different Colors

I have a question about my theme for https://styledsheet.com/

When I view the site on my computer or laptop, it displays as I intended it to. When I view the site on my parents computer, however, the colors are very grey (and not dark blue/purplish as I intended).

My parents computer is newer, and displays colors correctly on every other site I visit on it. Doesn’t matter if I use ff, or ie, the colors are always real dull.

What colors do you see? Grey/dullish, or dark blue/purplish?

Does anyone know how I can fix this?

Thanks!