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