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