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