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