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