Determination of a grid structure for a set of values in a device color space, in which heuristics are applied to a collection of color sample data in order to determine the structure of a look-up table that best fits the samples. Sampling data is sorted for each channel thereof, and the number of steps in each channel is counted. The data is checked for completeness. Steps are removed if they do not correspond to steps on the axes of a three-dimensional cube. If, as a result of step removal, a full LUT has been obtained, then the structure of the LUT has been determined and the process ends. On the other hand, if a full LUT has not been obtained, then steps are removed if they are under-correlated with other steps.