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