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