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