The authors present a novel extended color space for low-dimensional spectral color management, coined LabAB. They discuss design goals and perform a comparison of several approaches to fuse the perceptual information engendered by several illuminants. Results indicate that, with only five dimensions, LabAB conveys significantly no less perceptual information on average than state-of-the-art representations such as the interim connection space LabPQR. They also demonstrate that LabAB can be used for spectral vector error diffusion.