One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,3,6,4,5,7,8)(10,15,16,30)(11,19)(12,24)(13,26)(17,35,34,39)(18,36,28,33)(20,25,32,31)(21,27)(22,40)(23,29)(37,38)(9,10)(11,20)(12,25)(13,28)(14,16)(15,29)(17,24)(18,26)(19,30)(21,34)(22,35)(23,32)(27,31)(33,38)(36,40)(37,39) involution — undirected(2,5)(6,8)(10,16)(15,30)(17,34)(18,28)(20,32)(25,31)(33,36)(35,39) involution — undirectedA Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.