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