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