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