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