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