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