I see on many photos the center caps are darker on the 71 cars. But in photos of the 70 cars with rallys it seems the center cap is same as rim or a bit darker but not as dark as 71. what is correct for the 70 same as rim ? or ?

1970 were light textured argent, 1971 were darker textured argent. The rallye wheels (all years) were NON textured silver (which is also called argent but is just metallic silver). The key is the meaning of argent, which in French means "silver".