Many species in any group of Animals use to defend themselves acquiring colours, shapes and movements of their habitat. This is the way they use to become virtually invisible to their predators. It is true in any kind of habitat, in the sea, in a rain forest or in a desert.

Many Buprestidae are cryptic. A large part of them use green colours to imitate leaves. Especially in wet tropical countries their bright green colour allows them to mingle with the dewy vegetation. But the same colour is used in temperate zones by some species.

Evides sp. - Photo by Chuck Bellamy
Melanophila picta decastigma

Many other Buprestidae have a brown, grey, copper colouration, very similar to the bark of trees where they spent a lot of their time of reproduction. Some of them use to turn around trunks and branches to hide themselves when they perceive a predator, or an entomologist!

Others (Julodis) stay hanging to small branches of bushes; so they stay in the shade (it may be very usefull in very hot places) and are less visible to birds and it's possible they are mistaken for fruits.They can also try to save themselves falling in thanatosys (I can assure it's not easy to see a motionless and dusty Julodis near a bush on the ground covered with dried leaves, seed, dust, etc.). 

Julodis aequinoctialis
Latipalpis plana

Many species, evolved to be less visible among leaves, become easy to see when stay on a trunk to reproduce, but usually this happen in a very short time. 

Many species use cryptic colouration, brown, grey, black, etc. on their dorsal side (head, prothorax and elitrae) and  bright colours for their abdomen and ventral side, so they can hide themselves when they stay on a bark, but they can become visible to the other sex if they need. Like among many lepidoptera, these species become bright and easy to see when they are flying (the body, under their elytrae, is always bright, usually green/blue or golden), but dark and cryptic when they stop on trunks or barksWe can observe some of these species in any Fauna, but they are particularly in evidence in Madagascar, where we can find a lot of species of Polybothris showing this adaptation.
Polybothris pandus
Polybothris pandus

Polybothris pandus: dorsal and ventral view

Polybothris auriventris
Polybotris auriventris
Polybothris auriventris: dorsal and ventral view

There are also few Polybothris with bright colours underside and upperside:

Polybothris sumptuosa gema
Polybothris sumptuosa gema
             Polybothris sumptuosa gema: dorsal and ventral view

There is another way to confound the sight of a predator, usually a bird: showing a disruptive colouration. It is obtained with stripes or large spots of very different colours to make hard to understand where a body start and where the same end. It's well known in many Vertebrates and zebra is probably the best known species using it. But it's also used by Buprestidae, especially several Indomalaysian species. Here, we can see few examples, all in subfamily Chrysochroinae:

Chrysochroa buqueti Chrysochroa ocellata ephyppigera Chrysochroa mniszechi
Chrysochroa bouqueti - Thailand
Chrysochroa ocellata ephippigera - Malaysia
Chrysochroa mniszechi - Thailand
Chrysochroa corbetti
Chrysochroa lepida
Agelia peteli
Chrysochroa corbetti - Thailand
Chrysochroa lepida - Namibia
Agelia peteli - Zimbabwe