Gel paste food colours: Electric pink, lemon yellow, sky blue and regal purple
Pastel coloured Sprinkles
Lightly whisk egg white and lemon juice together in a bowl. Gradually add icing sugar, whisking until smooth and combined.
Divide the icing mix equally between 4 bowls.
Tint each bowl with two to three drops of each of the food colours, and mix to combine. The colour of the tinted icing should be pale.
Using a small palette knife, spread a small amount of the pink icing to start with over the Cafe Cookie, and repeat with the rest of the colours. Swirl the icing colours slightly to blend the edges together.
Sprinkle over the pastel coloured sprinkles, and leave to dry.