The mechanisms of color formation in porcelain containing neodymium oxide, which can change the color by means of the absorption or reflection spectra, depending on the light source, are studied. The optimal content of neodymium oxide in porcelain is determined in the 1976 CIE system, the optimal neodymium oxide content in porcelain is determined, and the dependence of the color of articles on the firing medium and light source is determined.Among the many groups of porcelain articles, hard porcelain with different variants of decoration is now widely used. Artists and designers who use hard porcelain need subglaze paints and pigments, which are also used for coloring ceramics. The number of articles (mainly articles manufactured abroad) with a colored ceramic mass -both single-color and with color variations (the interior of an article is one color and the exterior is a different color) -is continually increasing. Such porcelain is characteristic for china and large decorative interior articles (vases, pots for plants, plaques, panels, and so forth).Oxides and pigments are used in subglaze decoration of porcelain. A few oxides are heat resistant in the firing temperature range of porcelain articles 1350 -1410°C and in a reducing gaseous medium so that the subglaze color palette for hard porcelain is sparse. It is well known that chromium, manganese, and cobalt oxides withstand such firing conditions.Pigments containing iron, titanium, copper, nickel, and other oxides as colorants are also used for subglaze painting on porcelain. High-temperature coloring compounds must be used for subglaze paints for solid porcelain. Such compounds are rare-earth element oxides (REEO). REEO can be used as components of paints for decorating porcelain articles and as a constituent of paste that can color porcelain. A pigment that can be used to color hard porcelain must meet two main requirements: it must be stable in the temperature interval 1300 -1410°C and it must not change color in the range of the oxidation-reduction potential (ORP) of the gas medium used for firing porcelain.It is known that ceramic pigments of the Nd 2 O 3 -Al 2 O 3 system are used as subglaze paints for porcelain and glazed pottery as well as in majolica. Such paints are heat resistant, withstand well firing temperatures in the range 1140 -1350°C, do not give pinholes, dry areas, clumping, and other defects on glaze, and produce very pure and soft rose-lilac tones.The process of synthesizing ceramic pigments with equimolecular ratios of the oxides (Nd 2 O 3 : P 2 O 5 , Nd 2 O 3 : ZrO 2 , Nd 2 O 3 : TiO 2 ) has attracted interest in recent years. For such oxide ratios it is possible to obtain pigments with different palettes suitable for coloring glazes [1].The known temperature dependence of the standard value of the Gibbs formation energy of certain oxides possessing a coloring effect [2] makes it possible to evaluate the reduction of metal oxides in a gas medium with a high CO content (2 -5% 2 ). It is evident that REEO cannot be reduced by carbon mono...