Question

what colour does lichen turn in a basic solution

Answer 1

Litmus is a natural dye extracted from lichens. It is the most commonly used natural indicator.
Litmus turns acidic solutions red and basic solutions blue. 

Answer 2

lichen is a organism like fungus , it is used to make the natural indicator,the litmus.the color of the litchen is puple.

if it put in base , the colour becomes blue