it is usually said that the Kendall-Ball-Harvey midfield was so well balanced which I take to mean that one player did the running, one the tackling and one the passing (or something like that). I always thought that was wrong and that each of the three was balanced. All three could defend and tackle, all three could run, all three could pass (though only Ball was a regular scorer, Kendall scored a few, Harvey not many). Also in those days midfield players were usually categorized as workers/consistent/limited or skilful/flair/inconsistent. These three fell into both categories except the inconsistent.
Harvey's particular talents were short passing, long passing, tackling, running back to help the defense and covering the whole of the pitch except perhaps the opposition penalty area. He was incredibly consistent, hardly any poor games, and in most games he was always one of the Everton's best players. Of his contemporaries the player he most reminded me of was Billy Bremner (without the goals and without the temper). Of more recent players Xavi of Barcelona reminded me of Harvey in the way he kept the ball moving from teammate to teammate with a stream of accurate passes, usually simple and short but sometimes long and penetrating.
One last thing. I always thought of Colin Harvey's playing type as a cross between Alex Young (stylish and graceful) and Alan Ball (relentless and dynamic).