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