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