Colloquialism as a noun is a colloquial word or phrase; a common spoken expression, often regional. while Dialect as a noun is a variety of a language (specifically, often a spoken variety) that is characteristic of a particular area, community or group, often with relatively minor differences in vocabulary, style, spelling and pronunciation.
Part of speech: noun
Definition: A colloquial word or phrase; a common spoken expression, often regional.
Part of speech: noun
Definition: A variety of a language (specifically, often a spoken variety) that is characteristic of a particular area, community or group, often with relatively minor differences in vocabulary, style, spelling and pronunciation.
We hope you now know whether to use Colloquialism or Dialect in your sentence.