A wide color gamut (WCG) display has great color rendering capability and offers the opportunity to achieve a pleasing and realistic appearance in terms of image quality. To take full advantage of the large display gamut, a new gamut extension algorithm (GEA) is proposed based on a new color appearance scale, vividness. The performance of the new GEA was investigated via a psychophysical experiment together with five commonly used GEAs. In addition, two different uniform color spaces (UCSs) were also studied including the CAM02-UCS color space and a space, Jzazbz, designed for high dynamic range (HDR) and WCG applications. The results showed that the newly proposed GEA, i.e. the vividness-extension (VE) algorithm, outperformed all the other GEAs and the Jzazbz space was a promising UCS for evaluating gamut extension.