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)(27,29)(28,36)(30,31)(32,34)(33,38)(35,37)(39,40) involution — undirected(1,2)(3,7)(4,8)(5,6)(25,26,30,31)(27,32,34,29)(28,33,38,36)(35,37,40,39)(10,15)(11,18)(17,20)(19,24)(26,31)(27,34)(33,36)(35,40) involution — undirected(1,3,5,4)(2,7,6,8)(9,11,14,18)(10,16,15,13)(12,19,22,24)(17,23,20,21)(25,27)(26,32)(28,35)(29,31)(30,34)(33,37)(36,39)(38,40)(1,4,5,3)(2,8,6,7)(9,12,14,22)(10,17,15,20)(11,19,18,24)(13,21,16,23)(25,28)(26,33)(27,35)(29,39)(30,38)(31,36)(32,37)(34,40)(9,13,14,16)(10,18,15,11)(12,21,22,23)(17,24,20,19)(25,29,30,32)(26,27,31,34)(28,37,38,39)(33,40,36,35)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.