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