Students embarking upon a colour chemistry course usually approach it by way of a general introduction and proceed to more detailed treatment of the subject when they have acquired some knowledge of its character and scope. This book has been written with the twofold purpose of serving as a guide to such students during the introductory part of their course and of supplying the needs in this field of others whose main interest is in a related branch of technology or pure chemistry. An attempt has been made to present the main features of the subject in an easily assimilable form. The great amount of published information renders the choice of material for a short book somewhat difficult, and I am keenly conscious of topics that might be thought worthy of more extensive treatment. However, a concise account cannot be comprehensive, and suggestions for further reading are provided at the end of the book. The chemistry of colouring matters can be regarded as a branch of pure chemistry, but the development of knowledge in this field has followed a course determined chiefly by the applications of dyes and pigments. It has therefore appeared appropriate to treat the subject here as a branch of technology.