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