The author could have said the facts and left it very straight forward so she could move onto the plot. The author, instead, used this section as an opportunity to give descriptive elements in order for the reader to become better aware of the time period or setting, or to be better acquainted with the characters. Colour (in this case) = entertaining information, yet helpful to forming atmosphere and adding charm

"Adds a little colour" is basically the same expression as "Shed a little light." It means to illuminate or clarify a subject by supplying more details.

Meaningless details, such as the new TV is flat and improved graphics, when what matters is how flat it is or how good the graphics have gotten. Or like the horoscopes, generalize information

adds a little colour = gives a few details