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