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