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