Each cryptographic represents a piece of text. It's a grid, where the arrangement of colours in each square corresponds to a characer. To work out what a cryptographic contains, you must first "read" it, and translate the grid of squares, reading left-to-right and top-to-bottom, into a string of characters.
At the top left of each cryptographic is a square that contains all four coloured triangles. This is the colour indicator, and before you start you need to find it. One colour may be the background colour of the artwork so it may appear to be transparent.
Adjust the colours in the key below to match the colours in your cryptographic.
Now, "read" the cryptographic from top left to bottom right as you would a page. Consult the key, and match each grid square to a character.
You can make cryptographics with or without a password. If you're lucky, you're done, because the text you just translated will be readable. If it looks like junk, it has been encrypted with a password.