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