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