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