The marbling effects come in the same set of colours as the eggs, so if you happen to get the same colour egg as marbling (or a close colour) it may not be very visible. However it still counts towards your completed egg, and you do have some control over the colour of your egg/marbling if you wish, as both of those depend on the colour of the wildlife which dropped them.
Tbh, it is difficult to get these mix-n-match style releases right - there are often some combos that don't work so well together
Post by Fairyland Developer