Why are links blue and purple?

In the 90s, due to a misunderstanding of how indexed color displays worked, it was popular to prefer colors with hex triplets with their digits duplicated (i.e. #03F is a shorthand for #0033FF) in steps of three (0 3 6 9 C F), or, expressed as factors of 256: 0, 0.2, 0.4, 0.6, 0.8, 1.

These colors weren’t really any safer since they’d be double-quantized on different palettes. Thankfully this dumb “web safe colors” myth died when 24-bit displays became affordable.

For all you retro- and permacomputing lovers out there, the traditional VGA/CGA colors instead uses these steps: 00, 80, C0, FF. That creates 64 colors but they selected sixteen from them (so it could be indexable by four bits). Out of these sixteen, blue (#0000FF), navy (#000080) and purple (#800080) are good candidates for link color. You want it readable with dark foreground text, you couldn’t go gray because the background was gray (for some reason), you want two colors that sorta match each other but are different. Out of these three, they selected blue and purple.

These days, the WHATWG recommended colors are #0000EE blue and #551A8B purple, but they don’t explain why.