Dark color on codes problem

I’m reading How to Design Programs using DrRacket.

When I wrote the following codes as

(define (sign x)  (cond  [( > x 0) 1] [( = x 0) 0] [( > x 0) -1])) 

then I get dark color on codes as following

enter image description here

Why did I get it? Can you explain it? Thanks

Note: I’m new here if the tag is false, then can you edit? And can you help with tags?