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)(11,15)(12,23)(13,21)(14,19)(16,18)(17,28)(20,25)(22,32)(24,27)(26,36)(29,30)(31,34)(33,39)(35,38)(37,40) involution — undirected(2,5)(3,7)(9,11,15,10)(12,24,27,23)(13,21,16,18)(14,30,32,34)(17,25,20,28)(19,31,22,29)(26,33,40,35)(36,38,37,39)(1,3,4,7)(2,6,5,8)(9,12)(10,17)(11,20)(13,25)(14,26)(15,27)(16,28)(18,24)(19,33)(21,23)(22,35)(29,38)(30,36)(31,39)(32,40)(34,37)(2,5)(6,8)(9,13,15,16)(10,18,11,21)(12,25,27,28)(14,31,32,29)(17,24,20,23)(19,30,22,34)(26,39,40,38)(33,36,35,37)(9,14,15,32)(10,19,11,22)(12,26,27,40)(13,29,16,31)(17,33,20,35)(18,34,21,30)(23,36,24,37)(25,38,28,39)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.