Just you know amber is a lager color, Vienna Lager, Czech Amber, Marzen, Dunkles Bock, International Amber Lager (usually a Mexican amber) are all styles that are amber lagers, just as there are dark lagers. But your issue is you tried to brew a pale lager but it is darker.
So as others have said, it could be oxidation or if you used extract, it can be darker...but one other question...are you saying it looks darker in the fermenter, or is it darker after bottling? Light beers will look darker in the fermentation vessel due to less light refraction (light shining through the liquid) and due to yeast in suspension. So if you are talking about in the fermenter, give it a few weeks and then take a sample and you will see that it is much lighter than what it looks in the jug.