What is the effect of an alkali on litmus paper?

An alkali is a basic substance that has a pH greater than 7. When litmus paper, which is a pH indicator, comes into contact with an alkali, it undergoes a color change to blue. This is due to the alkali's basic nature, which causes the litmus dye to shift its color response. In contrast, acids would turn litmus paper red. Therefore, when using litmus paper as a tool to identify the presence of alkalinity, the expected and correct outcome is a shift to blue, confirming the basic nature of the solution being tested.