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