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