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