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