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