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