As Eric Stoller notes, this is a perfect set up for a study of the socialization of gender. Boys draw fire engines! Girls draw ballerinas!
The inanity in this exercise is even more clear because I'm going to guess that the publisher decided to make the "boy's" red and the "girl's" blue to de-emphasize the ridiculous stereotypes being employed. However, all it does is underscore those ridiculous stereotypes. Blue did not always equal boys and pink did not always equal girls. In fact it used to be just the opposite:
When colors were first introduced to the nursery in the early part of the 20th century, pink was considered the more masculine hue, a pastel version of red. Blue, with its intimations of the Virgin Mary, constancy and faithfulness, was thought to be dainty. Why or when that switched is not clear, but as late as the 1930s a significant percentage of adults in one national survey held to that split.
Pseudo science can try as they might, but these are not "natural" tendancies. They are taught from day one.