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