This has happened to me at least 15 times this week:
So I'm looking up recipes in JEI, then I find a bug so I switch to cheat mode to get some uncraftable items from our mod. Then I try to view some recipes later on and then boom, items are now in my inventory because I forgot to switch back.
Something like this would be really helpful. Obviously there doesn't need to be a [Normal Mode] text, just the cheat one.

It might look better if there was maybe a red icon overlayed on the settings icon in the bottom right or the page numbers at the top change color based on mode
Well it needs to be noticeable, or else it would be completely useless.
It needs to be subtle, or else it would be completely hideous :D
IMO the way I edited the text into the image above makes it noticable and still keeps it clean. Or even something as simple as making the page numbers red and bold would work.
I'm with mezz on this one, if the change is small but not entirely unnoticeable it should get the job done without distracting from the item list, UX should be the primary concern here
Personally I find the primary concern function. Looks are a bonus.
This project tries to keep a minimalist design to some extent, there are no words anywhere on the item list.
Like I said, simply making the page numbers red and bold could keep the minimalistic design by not adding any new objects to it, and it could get the point across.
That would be better, but it would be confusing if you didn't know what it meant already. I haven't thought of a good solution but I will leave this open.
Maybe a retexture of the wrench would indicate that your mode is different.
From a user standpoint I do think that adding a light grey text to the search box stating the mode that you are in might do the trick
Either changing the wrench or the outline color of the search bar.
Can we agree that this red wrench does the job?

Yup looks good!
Yeah, it looks nice but still not terribly obvious and it probably won't stop me from accidentally cheating items when looking up recipes. Maybe a bit more saturated red?
Any more obvious and it'll just become an eyesore IMHO
The more red I make it the darker it gets, maybe I need to make a new asset instead of messing with OpenGL colors.
This might be good

Is it possible to make a red mouseover highlight as well? That'd certainly be very clear in function
Compromise?

The latest 1.9 build has it (I assume that's what you're using).
Yep. Thanks ;)
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Can we agree that this red wrench does the job?