IIRC, Dan Connolly, when he was at Convex, wrote an SGML viewer that used blue hyperlinks. He did this work in 1990-92. At the same time, he was collaborating

IIRC, Dan Connolly, when he was at Convex, wrote an SGML viewer that used blue hyperlinks. He did this work in 1990-92. At the same time, he was collaborating with Tim Berners-Lee in his spare time. So blue was in the air by then.