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