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