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