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