Method for transforming in a color transformer a first version of a color to be reproduced by a proof viewing device a into a second version of the same color to be reproduced by the same proof viewing device in a way that a first human observer perceives this color reproduced on said proof viewing device according to said second version as this color is perceived on a final color reproduction device by at least one second human observer, said method comprising: A/ Transforming device-dependent color coordinates (R P,G P,B P) adapted to control said proof viewing device P in order to reproduce said color according to said first version, into device-independent-and-observer-A-dependent color coordinates (X A,Y A,Z A) using a first color characterization model (M P-A) of said proof viewing device calibrated to the human visual characteristics of said first human observer; B/ Transforming said device-independent-and-observer-A-dependent color coordinates (X A,Y A,Z A) into device-dependent-and-observer-A-dependent color coordinates (R D,G D,B D) using a second color characterization model (M D-A) of said final color reproduction device calibrated to the human visual characteristics of said first human observer; C/ Transforming said device-dependent-and-observer-A-dependent color coordinates (R D,G D,B D) into device-independent-and-observer-B-dependent color coordinates (X B,Y B,Z B) using a third color characterization model (M D-B) for said final color reproduction device calibrated to the human visual characteristics of said second human observer which are different from the human visual characteristics of said first human observer; D/ Transforming said device-independent-and-observer-B-dependent color coordinates (X B,Y B,Z B) into device-dependent-and-observer-B-dependent color coordinates (R PB,G PB,B PB) using said first color characterization model (M P-A), said device-dependent-and-observer-A-and-B-dependent color coordinates (R PBA,G PBA,B PBA) being adapted to control said proof viewing device in order to reproduce said color according to said second version. A/ Transforming device-dependent color coordinates (R P,G P,B P) adapted to control said proof viewing device P in order to reproduce said color according to said first version, into device-independent-and-observer-A-dependent color coordinates (X A,Y A,Z A) using a first color characterization model (M P-A) of said proof viewing device calibrated to the human visual characteristics of said first human observer; B/ Transforming said device-independent-and-observer-A-dependent color coordinates (X A,Y A,Z A) into device-dependent-and-observer-A-dependent color coordinates (R D,G D,B D) using a second color characterization model (M D-A) of said final color reproduction device calibrated to the human visual characteristics of said first human observer; C/ Transforming said device-dependent-and-observer-A-dependent color coordinates (R D,G D,B D) into device-independent-and-observer-B-dependent color coordinates (X B,Y B,Z B) using a third color characterization model (M D-B) for said final color reproduction device calibrated to the human visual characteristics of said second human observer which are different from the human visual characteristics of said first human observer; D/ Transforming said device-independent-and-observer-B-dependent color coordinates (X B,Y B,Z B) into device-dependent-and-observer-B-dependent color coordinates (R PB,G PB,B PB) using said first color characterization model (M P-A), said device-dependent-and-observer-A-and-B-dependent color coordinates (R PBA,G PBA,B PBA) being adapted to control said proof viewing device in order to reproduce said color according to said second version.