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