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