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