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