One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,6)(4,5)(7,8)(9,10,14,18)(11,21,23,17)(12,24,26,32)(13,19,27,33)(15,29,16,20)(22,37,38,31)(25,40,39,34)(28,36,30,35)(2,5)(3,7)(9,11)(10,17)(12,15)(13,25)(14,23)(16,26)(18,21)(19,34)(20,24)(22,30)(27,39)(28,38)(29,32)(31,35)(33,40)(36,37) involution — undirected(9,12,16,11,14,26,15,23)(10,17,29,32,18,21,20,24)(13,25,30,22,27,39,28,38)(19,31,36,34,33,37,35,40)(2,5)(6,8)(10,18)(17,21)(19,33)(20,29)(24,32)(31,37)(34,40)(35,36) involution — undirected(1,3,4,7)(2,6,5,8)(9,13,14,27)(10,19,18,33)(11,22,23,38)(12,25,26,39)(15,28,16,30)(17,31,21,37)(20,35,29,36)(24,40,32,34)A 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.