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