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