grayer / greyer are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
grayer: NA
greyer: (adjective) of an achromatic color of any lightness intermediate between the extremes of white and black. (adjective) showing characteristics of age, especially having grey or white hair; -Coleridge. (adjective) used to signify the Confederate forces in the American Civil War (who wore grey uniforms). (adjective) intermediate in character or position.
grayer: g·r·EY·er
greyer: NA
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)