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