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