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