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