Monitoring fuel mixture by looking at spark plug insulator color is a practice that went obsolete over 40 years ago. Unless you're running leaded gasoline, which gave the "tan to chocolate brown" color we looked for on Fred Flintstone's car, plugs go from white to sooty black without giving any useful information about fuel mixture. Go ahead and look for it, but it's going to be like finding a chicken with lips!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!