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