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