What is the rhyme scheme for an acrostic poem?

Acrostic poems don't have a traditional rhyme scheme in the sense of rhyming lines. The "rhyme" is created by the first letter of each line spelling out a word or phrase vertically.

For example:

Sunshine warms my face,

Nature's beauty I embrace.

Outside, the world's a stage,

Where wonders I engage.

In this example, the first letters of each line spell out "SNOW".

While there isn't a specific rhyme scheme, you can still incorporate rhyming within the lines themselves to add a musical quality.