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