One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(5,9)(8,10)(12,15,16,17)(13,20,18,21)(14,23,24,25)(19,22,26,27)(6,11)(8,10)(12,14)(13,19)(15,23)(16,24)(17,25)(18,26)(20,22)(21,27) involution — undirected(2,3)(4,6,7,11)(5,8,9,10)(13,18)(19,26)(20,21)(22,27)(2,3)(4,5)(6,10)(7,9)(8,11)(12,13)(14,22)(15,21)(16,18)(17,20)(19,23)(24,27)(25,26) involution — undirectedA 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.