You are a chameleon, i.e. very changeable- shifting according to the opinions of others, as the chameleon changes its hue to that of contiguous objects.
As the chameleon, who is known To have no colours of its own, But borrows from his neighbour's hue, His white or black, his green or blue.
Pliny tells us that Democritus wrote a book on superstitions connected with the chameleon.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894