When we look at the incredible array of colours that fill our world today we are perhaps unaware that conjugation plays a major part in them.The pigmants that are responsible for this are the compounds with many double bonds.The colours that appear are only able to do so through conjugation.
The majority of dyes and pigments are highly conjugated compounds.However there are certain rules that are obeyed.If there are fewer than 8 conjugated double bonds,the compound absorbs the ultraviolet part of the spectrum and the difference is not visible to the naked eye.If however more than 8 are absorbed the difference is noticed and after 11 conjugated double bonds red is visible.Blue and green are only visible if a hughe number of conjugated double bonds are absorbed.
The compound that is reponsilble for the colour in the things we see is called a chromophore
Some examples of the pigments are shown below
The compound shown above is the structure reponsible for the blue pigment in jeans and denim in general