Coursepress is not "retina"-friendly (Simplylearn)

The icons used in the Coursepress do not look good on my Macbooc pro. They are not sharp and retina friendly, and the same thing happens with the logos I use as the header logo on the different pages.

Why does this happen? Can you update the logos and the resolution?
And can you make it an option to make the icons black or of a customizable color?