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