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