Re:What about die color? (Score 5, Informative)

The green/amber part you were looking at may have been a protective coating applied when the microprocessor was packaged. Regardless, microfabricated chips can indeed be technicolored marvels.

Most materials used in microfabrication are either transparent (insulating layers) or grey (metallization), but resulting devices can appear coloured due to optical interference. Colours present in structures of a microfabricated device are related to the thickness and composition of the patterned thin-film coatings that form the device. For a single thin film, thickness can be determined from, for example, the Michel-Lévy interference colour chart if the birefringence of the thin film material is known. Variations in colour across a film indicate non-uniform thickness. The colour resulting from several layers of patterned thin-films is more complex to predict, but the same basic principles apply.