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