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