Okay....so, I'm going to go ahead and state the obvious and say that the colors on the picture correspond to specific parts of the "board", namely where the matching-colored arrows are. But, it doesn't seem that anything on the Joker matches the blue-colored arrow...

Blue=?
Green=irises, background behind head, hair(this one doesn't look like it matches up exactly, though...)
Yellow="whites" of eyes, collar
Red=top background
Purple=gums, shirt
Black=lips, eyebrows, eyelashes

And there are six arrows, and six previous riddles, so because we need the answers to all of the previous ones, perhaps each color also corresponds to a previous puzzle? Like the light green = Poison Ivy, and the red = Harley? ...maybe?

** SPOILERS **
This post will reveal the entire worked solution to this riddle -- as well as the solutions to all six previous riddles.  If you're still working on any of the riddles in this game, stop reading here!

The Riddler warns us that we'll need the answers to all six of his previous riddles to solve this one.  In reality, we can probably do it with only three or four with the help of some Internet search tools, but having all six answers would sure help.

To review, the answers were:


--spoiler space--


Poison Ivy: CONAN
Catwoman: ANTMAN
Two-Face: PUMPKIN BOMB
The Penguin: GIBBIFER CALIFORNICUS
Scarecrow: PIXAR
Harley Quinn: NEIL GAIMAN

Looking at our diagram, we see interlocking hexagons accompanied by six colored arrows.  We might expect to fill in our riddle answers along the lines of hexagons indicated by the arrows.  The problem is that most of them don't fit anywhere.  Certainly we're not going to squeeze GIBBIFER CALIFORNICUS into that grid.  So we're still missing something.

Some of the riddle answers might strike us as having something in common.   Conan and Ant-Man are comic book characters.  Pumpkin bombs are a comic book weapon.  Pixar made a comic book movie, The Incredibles.  Neil Gaiman has written comic books.  We may not be sure what to do with Gibbifer californicus, but we detect a theme.

The Riddler helps us out.  “All the capes are assembled,” he writes.  And the Joker is a “colorful character.”  So we're thinking about comic books and colors and looking at these riddle answers – maybe checking the unfamiliar ones on Wikipedia.  Sooner or later, we get the big Aha moment: each riddle solution uniquely clues a color-coded comic book character.  Conan's companion and spinoff is Red Sonja.  Ant-Man is the same Avenger also known as Yellowjacket.  Pumpkin bombs are used by the Green Goblin.  Gibbifer californicus is quite literally a blue beetle.  Pixar created the superheroine Violet Parr.  And Neil Gaiman's second-best-known comic book is named Black Orchid after its protagonist.

Now we get it.  After the red arrow, we should fill in SONJA; after the yellow arrow, JACKET; and so on.  Satisfyingly, we discover that the grid links together as expected.

All we have to do now is read off the shaded hexes in order from 1 to 12.  They spell out the word BANDERSNATCH – and that's the password to disarm the bomb.