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