Shabbos Treasures 36 - Colouring & Dyeing

Question 1) Is it OK to add food colouring to water for decorative purposes? Question 2) Can you use a toy fork that will change colour, eg when touching ice cream? Question 3) What about using lipstick? Question 4) Can you spill dark juice on a white table? Question 5) Pinching a kids face that turns red, ok? Question 6) Wearing eyeglasses that darken in sunlight? Question 7) Invisible ink? The melacha of dying was necessary for the manufacturing of the special curtains and tapestries of the mishkan. Colouring of any materials or substance is the melacha whether accomplished by changing the colour of the material or by adding a coating to it. Even darkening an existing colour is problematic. Any material is included, including painting a wall, adding food colouring for decorative purposes etc. Even if the colour will fade after a while on it's own its still not ok to use, eg cosmetics like lipsticks, eye shadows etc or kids toy plastic cutlery that changes colour with heat/cold. To be the melacha it must entail a measurable change to the surface itself, so to pour dark juice on a white table is ok as there is no meaningful change to the surface. If the colouring is brief and unintentional it's ok, eg to pinch a kids cheek. It would be ok to sit outside on a hot day even though one could become tanned as it's unintentional. If brief colouring occurs indirectly its ok even if intentional, so you can wear photo gray lenses, even though the purpose of them is to become darker with sunlight as the colouring is indirect and subsequently disappears when you return indoors. There are other reasons it's ok too, including that it's  purpose is a protection from the sun and not to create any colouring effect. Invisible ink or dye is not ok