The invention comprises dyes which have at least one group of formula N(R)T where R is H or an alkyl or cycloalkyl radicle, which may be substituted, T is a pyrimidine ring attached to N through a C atom of the ring and has at least one SO3H group in the form of an alkali metal, alkaline earth metal or magnesium salt, each of the SO3H groups being attached to a C atom of the pyrimidine ring. The dyes may be made by reacting dyes containing a corresponding group N(R)T1, where T1 is an appropriate halo-pyrimidine ring, with a metal salt of sulphurous acid, by conventional processes of diazotization and coupling, or by reacting dyes containing an N(R)H group with the required halopyrimidine. Group N(R)T may be attached to a carbon atom in the dye molecule which is part of an aryl residue or of an alkyl chain, which chain may be directly, or via a bridge, attached to an aryl nucleus. Preferred dyes are azo, e.g. mono- and polyazo, nitro, anthraquinone and phthalocyanine dyes. Water-solubilizing groups, e.g. alkylsulphone, sulphamyl, carboxylic acid and preferably sulphonic acid groups, may be present. Metal complexes, e.g. of Cu, Cr and Co, may also be made. Mg, Ca, Ba, K and Na are metals specified for salt formation, salts of alkali metals being preferred. Indicated as groups which may be attached to the pyrimidine residue, other than SO2H, are halogen, alkyl, aryl, carboalkoxy, nitro and cyano groups. Representative of indicated values for R are methyl and butyl, which may contain hydroxy or methoxy groups, and cyclohexyl. Bridges mentioned are O, S, NH, N alkyl, SO2, SO2NH, CONH and SO2N alkyl. Dyes of the following classes are indicated as starting materials <FORM:0942796/C3/1> where D1 is an at most dicyclic aryl radicle, which is free from azo and NHR groups, the NHR group is preferably attached to the 6, 7 or 8 position and an SO3H group may be in the 5 or 6 position; indicated for D1 are benzene or naphthalene residues free from azo groups, stilbene, diphenyl, benzthiazolylphenyl and diphenylamine residues, preferred being sulphonated phenyl or naphthyl residues with the SO3 group o to the azo link, and the NAR group may be attached to the nucleus of a benzoylamino or anilino group which is in the 6, 7 or 8 position; diazo dyes of the formula immediately above where D1 is a residue of the azobenzene, azonaphthalene or phenylazonaphthalene series; monoazo dyes of formula <FORM:0942796/C3/2> where D1 is an at most dicyclic aryl radicle, preferably disulphonaphthyl or stilbene and the benzene nucleus may be substituted; mono- or dis-azo dyes of formula HN(R)-D1-N=N-K where D1 is an arylene residue, e.g. of the azobenzene, azonaphthalene or phenylazonaphthalene series or, preferably, an at most dicyclic arylene radicle of the benzene or naphthalene series, especially a sulphonated phenyl residue, and K is the radicle of a naphthol sulphuric acid or an enolizable ketomethylene compound with OH o to the azo group; dyes of formula D1-N=N-K2-NHR where D1 is as in the first two classes indicated above and K2 is an enolizable ketamethylene residue with OH o to the azo group; the metal complexes, e.g. Cu, Cr and Co complexes, of metallizable dyes of the above classes; anthraquinones of formula <FORM:0942796/C3/3> where an SO2H group may be in the 5, 6, 7 or 8 position and Y is a bridge, preferably a divalent radicle of the benzene series, e.g. phenylene, diphenylene or 4,41-divalent stilbene or azobenzene residues, and preferably Y has one SO3H group for each benzene ring present; phtholocyanates of formula <FORM:0942796/C3/4> where Pc is preferably a copper phthalocyanine residue, o is OH and/or an amino group whieh may be substituted, Y is a bridge, n and m are 1,2 or 3 with n+m not greater than 4 and dyes of formula NO2-A-NH-B-NHR where A and B are monocyclic aryl residues with NO2 o to NH. Preferred for diazotization are amines of the benzene or naphthalene series which may have arylazo groups and preferably the coupling components are of the acylacetorylide, 5-pyrazolone, phenol, naphthol or arylamine series. Preferred classes of dyes are those which contain a sulphonic acid group and one or two groups of formula -N(R)-T1(SO3H)Hlgn where T1 is a pyrimidine ring Hlg is Cl or Br and n 1 or 2 or one or two groups of formula <FORM:0942796/C3/5> where X is H or Hlg. The dyes colour natural and artificial textile materials, e.g. cotton, viscose rayon, regenerated cellulose, wool, silk, cellulose acetate, polyamides, polyacrylonitriles and aromatic polyesters. The dyes are of particular use for cellulose materials being applied in conjunction with an acid-binding agent. Nitrogen-containing textile materials are dyed from a mildly alkaline to acid dye-bath. The dyes are generally insoluble and are usually applied as an aqueous dispersion. Numerous examples are provided of the preparation of the dyes and their use in colouring processes to produce a variety of shades. The Provisional Specification describes dyes in which T is a pyrimidine ring attached to N via a C atom and which also has at least one group of formula -SO2Z where Z is OH or a substituted or unsubstituted hydrocarbon or heterocyclic residue, provided that the dyes have at least one SO3H group. Specifications 822,047, 822,948 and 891,601 are referred to.