Time is a black and white comic. There are no other colors that exist in the comic aside from some Mustard. Within the comic's world, though, there are a few colors mentioned.
In Frame 1714 Megan mentions green, "Well, it all gets greener further up."
In Frame 1746 Cueball mentions brown, "Brown and shiny. Kind of blotchy."
In Frame 2270 Megan mentions red, "I like it so much I'm coloring it a beautiful red."
Meaning of Colors MentionedEdit
According to sources online, the order that languages name their colors is usually this: black and white, then red, green and/or yellow, blue, and brown. After that purple, pink, orange, and gray get names (but not necessarily in that order, nor all of them).
So, according to this, the world of Time has advanced enough to at least the end of the first block of color names, which means that blue should also have a name. I'm assuming that they understand black and white (and not just because those are the colors we see). We don't know if they can distinguish the second block of colors, nor do we know if the Beanish people (or Rosetta's people, if different) distinguish all those colors or more.