What term describes an organism that carries an allele but does not show its effects?

Carrier Organism

Explanation:

When an organism carries an allele of any specific trait but do not express it , then it is called as carrier of that allele/trait. Such kind of patterns usually occur in a hereditary chain where one parent either a mother or a  father remains the carrier of an allele (usually an allele associated with some disease) which is not expressed due its recessive nature.

For example - Carrier of sickle cell disease.

The heterozygous allele pairs for normal traits such as color, height etc. with in an organism are also example of carrier organism that carries an allele but does not show its effects

colors do exist. the color of the sky is actually violet; humans percieve the color of the sky as blue.