[m0rti]

It is similar to why we chose gold to use as “gold” as humanity. Not all elements are suitable to be used as a store of value and physical currency.

Let’s look at the primary and secondary colours.

Yellow: Bad contrast. Red or Green: Action colours, would be bad to see them everywhere. Plus there might be accessibility concerns. Orange: Mostly used as “Not as urgent as red”. Purple: Not as neutral as blue, yet it is the second best option, that’s why visited hyperlinks are purple I assume. It is the logical choice.

We are left with the colour blue. Also, a plus that it is a primary colour; I would assume it is easier to display primary colours in earlier tech.