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