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