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