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