An alloromantic asexual (shortened to alloace) is someone who is asexual or ace-spec and also alloromantic. The term alloace is used because people often assume that all ace people are also aromantic.
The alloace flag was created by Tumblr user Varioriented-Pride on March 1st, 2019. It was inspired by the aromantic allosexual flag. There does not appear to by any specific meaning assigned to the colors, but the color red was likely chosen because it's the opposite of green, the aromantic color. White and purple were used to match the asexual flag.