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