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