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