The standard color then was chocolate brown. However white, gray and blue colored glazes could be ordered at additional cost as long as a minimum quantity of these special colors was requested.
Added note: A 90-year-old retired lineworker who lives locally (and is still youthful and very spry!) told me that they used to call these J-balls instead of Johnny Balls. Why? Because when working on the streets J-ball was far more appropriate in his day of linework when working(yelling or speaking) within the public, within neighborhoods and especially if women were around. In other words, J-balls were what were spoken when any customers might (or might not) have been around...as a courtesy and a habit, too...he added. There was nothing worse than a lineman yelling from above "Have you got any Johnny Balls down there?" in a quiet neighborhood. So, J-balls were the rule as he roved among line contractors here in the northeast from 1952-1995. As a kid the Brockton Edison Company crews I hung out with always called these insulators as "breakers". Same for all other local electric utilities I frequented. I do not know if that was policy or just plain lingo. However I never recall any utilities as a kid calling guy strain insulators as "Johnny Balls". Until I got well involved into the insulator hobby and that was after the late 60s, that nickname became known to me.