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