If they are hybrids then whatever the parent breeds might have produced will be possible, and any 'intermediate' shades too (ie if your hens are a cross between a breed which lays dark brown eggs, and one which lays white eggs, they can do ANYTHING from white to dark). Once you get to know the patterns you may start to see that one hen lays light brown eggs, one lays darker, and a third lays speckles. There is also a tendency for the last egg before a 'day off' to be a bit different from that hen's usual colour.
Hope this helps.