Dewey is the middle child with the blue color palette. He is often portrayed as the guts of the group. Because of this, he can arguably be considered the most mischievous.
In early cartoons, Dewey would sport a tangerine shirt instead of his now-trademark blue, which wouldn't appear in Dewey's animation days until DuckTales. In the 1987 DuckTales series episode "Duck in the Iron Mask", Dewey had an identity crises, as he wanted to separate himself from the trio to stand out as his own individual.
This is significant to Dewey's character in the 2017 reboot series.
In 2017's DuckTales, Dewey is adventurous and daring, but can take on more than he can chew. Due to being the middle child, Dewey loves attention and wants to be recognized as his own individual outside the trio.