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