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