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