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