Pastel(?): The currently used color scheme. I think "candy" would be a nice name for it.
Not all of the possible color schemes just change color:
Strings: This modifies the shape of the connections. Nodes are shown as a circle touching a line. L and FI are red, A and FOE are yellow, FO is blue.
Symbols: Nodes are shown as a particular symbol, related to their representation in the Strings scheme. FI and L are shown as empty arrowheads pointing towards/away from a line, A and FOE are shown as filled arrowheads pointing towards/away from a line, FO is shown as a circle near a line. They are also colored the same as Pastel.
Single node: Same as Symbols, but uses only a single node to represent each node in the underlying molecule. Results in sharp corners and smaller graphs. This is a significant change, and would require rethinking how moves are handled, as well as how to use the link tool.
Colors! Or lack thereof.
Not all of the possible color schemes just change color: