Yes, and in fact this change of skin colour between juveniles and adults is quite common. One of my favourite examples is the Emperor Angelfish (check out http://en.wikipedia.org/wiki/Emperor_angelfish for the radical change in colour).
Skin colour comes about mainly through swathes of pigment-containing cells in the skin layers. Depending on the environment in which these cells find themselves, their positions and pigments that they contain may change over time, resulting in an overall change in colouration. It’s a fascinating (and aesthetically pleasing) part of development!
It’s even true to a small extent in humans. Melanin pigment – which is the thing that makes your skin various shades of brown and also is what your tan consists of – can change over time. In babies, production of melanin often takes time to reach full speed, which is why people destined to have brown eyes may be born with them much lighter, even blue (blue eyes are made from the same black/brown/red melanin pigments as other colours, the pigments just scatter light differently when they are arranged thinly in the iris and look blue). It can take a few years for eyes to darken fully.
Melanin production increases at puberty too owing to hormonal stimulation, so we often get darker about then. It’s more semi-permanent than permanent though, because as we get older our ability to produce melanin gets impaired, and we lighten a bit again. Of course, this is just the base level of melanin, and as most people are exposed to the sun and spend lots of time either getting tanned or losing it, these smaller fluctuations in base levels go unnoticed.