This Spring Peeper (Pseudacris crucifer) was less than 1/2 inch and had the most stunning shimmering golden colours.They are very tiny, with a body length of only 1.7 to 3.2 cm (3/4 to 1-3/4 inch). The body color may be tan, dark brown, or even gray. The spring peeper has a darker "X" marking across the back.

http://en.wikipedia.org/wiki/Spring_Peeper