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