I like it as a starting point, a minor sidenote though: What you perceive and describe as bright red links, code and sidenotes is for me, as a color blind, almost indistinguishable from the body text if it wasn't for the underlines and monospaced font. Those off-black and red colors are for me just very similar dark hues on an off-white background. If you want to highlight these elements the current red does a poor job for colorblind people like me.
I'm colorblind as well, and did a little double-take when I read this comment, but I think you misunderstood. "Other forms of text—for instance, links and code—are slightly lighter and sidenote numbers are bright red to distinguish them from inline text." Only the sidenote numbers are bright red.
