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