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