I've only seen it on the WL cards. The weird thing is the white letter cards are missing the yellow printing, yet those flames have yellow in them.
In the regular version of the card (after a quick search) I found some very minor anomalies in that area, like these...
Ken-Brett-Gerry-Moses-(Names-in-Yellow)-2.jpgKen-Brett-Gerry-Moses-(Names-in-Yellow).jpg