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