Colour correction is the mapping of device-dependent RGBs to device-independent standard CIE XYZs. Due to the nature of colour image formation and the existence of metamerism, this mapping is inherently one-to-many and thus ill-posed. However, normally it is solved for through an error-minimising
linear one-to-one transform.In this paper we propose to make use of a definition of metamerism while maintaining the simplicity of a linear transform in defining an error-less colour correction. We say that a mapping is error-less if the RGB-XYZ pair put in correspondence through this
mapping is such that a real, physically realisable reflectance that induces this pair exists. We show how we can solve for such a mapping using constrained linear least squares optimisation. However, since this problem is highly constrained, we introduce a notion of error in our calculations,
building on a paramer set instead (the set of reflectances that map to a small uniform region in RGB space). We show that as little as 0.5% error is sufficient for a solution to exist.We find that the metamer set constrained linear colour correction works equally well as ordinary linear
least squares in terms of the mean and median CIE Δ