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