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)(11,15)(12,13)(14,16)(18,20)(22,23)(25,26)(27,35)(28,33)(29,34)(30,31)(32,36)(37,38)(39,40)(4,8)(6,7)(9,11,14,12)(10,15,16,13)(18,20)(22,23)(26,31)(27,36)(29,33)(37,40)(2,3)(6,7)(10,16)(11,12)(17,18,21,20)(19,23,24,22)(25,27)(26,32)(28,37)(29,38)(30,36)(31,35)(33,39)(34,40)(1,3,5,2)(4,7,8,6)(9,12,14,11)(10,15,16,13)(17,19,21,24)(18,22,20,23)(25,28)(26,33)(27,37)(29,31)(30,34)(32,39)(35,38)(36,40)(1,4,5,8)(2,6,3,7)(9,13,14,15)(10,11,16,12)(17,20,21,18)(19,23,24,22)(25,29,30,33)(26,34,31,28)(27,38,36,39)(32,40,35,37)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.