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