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