Figure 7 from Stockman, A. (2004). Colorimetry. In T. G. Brown, K. Creath, H. Kogelnik, M. A. Kriss, J. Schmit & M. J. Weber (Eds.), The Optics Encyclopedia: Basic Foundations and Practical Applications (Vol. 1, pp. 207-226). Berlin: Wiley-VCH.
CIE (1931) x, y chromaticity space showing the spectrum locus (continuous line) and spectral wavelengths at every 10 nm (filled circles). A representation of the color of each coordinate is shown, which is necessarily very approximate, since it is impossible to reproduce spectral lights in print.. For more details see here.
Stockman, A. (2004). Colorimetry. In T. G. Brown, K. Creath, H. Kogelnik, M. A. Kriss, J. Schmit & M. J. Weber (Eds.), The Optics Encyclopedia: Basic Foundations and Practical Applications (Vol. 1, pp. 207-226). Berlin: Wiley-VCH.