Well I really wanted to get a blue rectangular cooler to convert to a mash-tun but unfortunately I found a red one tucked away in my barn. I think I’m going to spray paint it so i can get that 110% efficiency that I keep reading about.
Red is faster dude, that’s why the insurance costs more.
SO thats the problem! Mine is green.
Won’t work, the plastic has to be completely infiltrated with the blue pigment for it to absorb the microwaves that destroy the glucose spontanogenerase. You might try covering it with foil, some people report good results with this shielding method.
What were you storing in this cooler in the barn? Sounds like it might be best suited for lambic production.
Don’t worry. You can compensate by boiling longer to get to 110%. 
My wife and I inherited an old farmhouse with a couple of large barns and every other week or so I go scouting around for things I could possibly use. A couple of months ago I came across a CO2 tank with a dual gauge regulator and a whole shank setup for a kegerator. The only usable thing is the tank unfortunately. I came across the cooler last week. It was empty when I found it. I keep looking for a trunk full of money but no luck yet.
Have you looked under the porch? Then again you might find a long lost relative… :o Cheers!!!
The best my blue one has done is low nineties. I have a silver one that’s 135% it’s size to convert now.