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