Here I have given the the slime mould Physarum polycephalum a choice of five different naturally pigmented bacterial pastes to eat.

Here are the results

Time 0: inoculation

Time 0: inoculation. the yellow central organism is the slime mould.

Time 12 hours:  At this stage, the slime mould has actively avoided yellow and blue, and ignored red and white as sources of food. If you look carefully, you can see plale slime trails, that are no longer occupied by the slime mould. These are areas of the agar that it investigated but which it found inimical or no source of food.Can yellow and blue be used as a deterent?

Time 20 hours: The slime mould has identified orange as a food source and is beginning to engulf and consume it.  If you look carefully, you can see plale slime trails, that are no longer occupied by the slime mould. These are areas of the agar that it investigated but which it found inimical or no source of food. Can organge  be used as an attractant?

Time 36 hours:   I felt a little sorry for the slime mould on its meagre diet of bacteria so fed it some oats. It’s very clear as to which food source it prefers at the momment