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