I googled this flag [I know, I know, that's 3.5 minutes of my life I'll never get back!] and found out that it was designed in 2014 by somebody called Cameron Whimsy.
'The main color, green, was chosen as it is the opposite of red, which is most commonly associated with romantic love. The two shades of green represent the aromantic spectrum, white represents platonic love and friendship, and grey and black represent the different parts of the sexuality spectrum.'
Aromantic flag - Wikipedia
That doesn't make a lot of sense: 'two shades of green represent the aromantic spectrum' means what? But don't panic, Whimsy explains it further:
Whimsy described the meaning of the stripes in further detail:
green-light green - the aro-spectrum (and aromanticism itself represented by green because green belongs to us now hell yeah). this covers every identity under the aro umbrella - demi, grey, lith/akoi, wtf/quoiro, cupio etc. EVERYTHING. even ones that don’t have names yet.
white - basically the ‘platonic’ stripe - friendship/platonic and aesthetic attraction/queerplatonic relationships/family, the importance and validity of all non-romantic relationships and feelings and non-romantic forms of love etc. etc. etc. etc.
black-grey - the sexuality spectrum - acknowledging aro-aces, aromantic allosexuals, and everything in between because we are a diverse lot.[4]
So 'green belongs to us now hell yeah' ?- try saying that out loud in Dublin on March 17th😉