Crested Geckos are found in several different colours namely:
BUCKSKIN - A gecko which is of a brown colour. The colour can be various shades of brown.
ORANGE - A gecko which is of an orange colour. The colour can be various shades of orange.
RED - A gecko which is of a red colour. The colour can be various shades of orange.
YELLOW/BLONDE - A gecko which is of a yellow colour. The colour can be various shades of yellow.
GREEN - A gecko which is of a green colour. The colour can be various shades of green however is normally an olive type of colour.
Any of the below morphs are compatable with any of the above colours.
Harlequin:

The Harlequiin Crested Gecko has a pattern on its back, sides and limbs which can be seen clearly in the picture above. Harlequins can be any colour however the pattern along the back sides and limbs will be a different colour to the rest of the gecko. The harlequin pictured above also has some dalamation spots.
Flame:

The Flame Crested Gecko is similar to the Harlequin in that there is a pattern along its back and the top of the head is the same colour as the pattern. The main difference here is that there is no or very minimal patterning along the side of the body and limbs.
Patternless:

The Patternless Crested Gecko pictured above is easy to identify. It is the same colour all over with no patterning at all. It can be one of any of the colours however the one pictured is a Buckskin.
Dalmation:

The Dalmation is another easy to identify morph. As you can see from the picture Dalmations have spots all over their bodies. Some Dalmations only have a few spots whereas you can get extreme Dalmations such as the one pictured which have many spots.
Pinstripe:

With a Pinstripe Crested Gecko the colours of the crests which run along the back are all the same colour. The colour is normally different the the colour of the geckos body. Pictured above is a very good example of a Pinstripe, you can see the that crests are all a uniform colour with no breaks.
Tiger:

The Tiger Crested Gecko has dark stripes on its back which carry on down the sides of the body.
Moonglow:

The rarest of all the morphs. Very rarely available in the UK. If you want one of these then your best bet is to find somebody willing to export one to you from the USA. As you can see they are all pale grey almost silver in colour.