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