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