The term is intentionally vague on what "neutral" means. However, it is specified to be inclusive of non-SAM aros, unit aros, aromantics who don't know if they experience sexual attraction, aromantics who can't distinguish sexual attraction from other types of attraction, and aromantics that otherwise take a neutral stance on their relationship to the allosexual-asexual spectrum. "Neu" can be expanded to neusexual or neutrosexual for those who want to use the SAM.
Aro neu was coined by Tumblr user A-romantic--aromantic on May 19, 2019.
The aro neu flag was designed by Tumblr user A-romantic--aromantic on May 20, 2019. The top half uses the same green stripe gradient as the aromantic flag. The bottom two stripes are a neutral mauve, which is in between gold for aromantic allosexuals and the purple for aroaces.
The color adjusted version was posted by Tumblr user arco-pluris on September 27, 2019.