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)(11,13)(12,17)(14,15)(16,18)(19,21)(20,22)(23,24)(25,26,30,31)(27,35,36,32)(28,33,37,39)(29,34,38,40)(2,6)(3,7)(10,15)(12,20)(13,16)(19,24)(26,31)(29,38)(32,35)(33,39) involution — undirected(1,3,5,7)(2,4,6,8)(10,15)(11,18)(12,20)(21,23)(27,36)(28,37)(32,35)(33,39)(1,4)(2,7)(3,6)(5,8)(9,11,14,18)(10,16,15,13)(12,19,20,24)(17,23,22,21)(25,27)(26,32)(28,34)(29,33)(30,36)(31,35)(37,40)(38,39)(9,12,14,20)(10,17,15,22)(11,19,18,24)(13,21,16,23)(25,28)(26,33)(27,34)(29,32)(30,37)(31,39)(35,38)(36,40)(9,13,14,16)(10,18,15,11)(12,21,20,23)(17,24,22,19)(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.