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