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