Natural cochineal dye of animal origin extracted from Dactylopius coccus was tested and used for the purpose of dyeing wool used to make a felt hat. Colour is defined as a psychophysical experience and conditions necessary to achieve the experience of colour are specified. The field of colour metrics is described as well as its meaning within the system of evaluation of colour, who was the first to introduce the assessment of quality and dimension of colour on the basis of three categories. The concept of dye and its uses are defined. Dyes are catgorized as natural and synthetic and natural dyes are classified according to origin in three categories. The terms for dyes of purple and crimson tones derived from cochineal bugs Dactylopius coccus and species Hexaplex trunculus are explained on the basis of their origin, definition of the animal species they are derived from, ways of cultivation of those animal species and methods of obtaining dyes from them as well as the use of dyes and their application methods. The meaning and the roots of the words "crimson" and "purple" are defined as well as the differences and similarities in meaning. Main characteristics of wool as a textile fibre are specified, as well as its specificities compared to other types of fibre and its behaviour in the felting process. Felting techniques are described as an ancient skills that can be regarded as part of the Croatian cultural heritage because it was used in times when clothing was made exclusively from wool. The technique of making air lace is described in detail. Although in itself very simple, the technique is nevertheless fairly demanding and requires a lot of time and effort. In this case air lace was used as a decorative addition to the felt hat. Hats have always had a special meaning in defining the status of a person within a society. The theoretical part of this paper provides an overview of the role of hats through history. Natural cochineal dye and wool as textile material were treated here within the dyeing process which was preceded by treatment with metal salts. The description is given of both the pre-treatment with metal salts and the wool dyeing process. The paper lists the process parameters and the instruments and devices used in the experimental part which is substantiated by the comparison of the results obtained. For a clearer understanding of the differences in the results of dyeing, the colour map of treated wool samples and the photographs of the finished felt hat including all the elements elaborated in this paper are provided.