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