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