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