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