She couldn't tell in the novel form either ^^While Killing Slimes for 300 Years, I Reached MAX Level Unknowingly (Manga) #12
...No, I can't tell the difference between a good slime and a bad slime when everything is grayscale.
Anyway, it's festival time! Our heroine's literally been there since the event's inception, such is the nature of longevity, but for reasons never directly participated. This time, since she has a family and all now, she decides to do something! And thus fantasyland gets its very first taste of a maid cafe, and we get the excuse to put the cast in maid uniforms. :3