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