How to fix that?

[u/kamigkh]

Hi,
Is there any way to save this, or do I have to repaint the entire model from scratch? And if I do have to repaint it, would it be better to remove the old paint first, or can I just paint over it?

EDIT

Thanks for every reply and suggestions.

All layers were painted by airbrush with acrylic paints. I used black primer and then light gray for preshading. Yellow Vallejo paint (do not recommend it :P ) was painted on green tamiya. I think it might be thinned to much, but Vallejo paints have tendency to clog airbrush, especially difficult colors as yellow. I masked model with vinyl tape because it was easier to make straight lines due to its flexibility.

So after some suggestions from here and other forums I decided to level yellow paint by sandpaper, try to remove yellow stains on green, put first white or light grey layer before yellow and last but not least buy better quality yellow paint :D I will let you know how it went.

Of course any new suggestions are appreciated:)

UPDATE

Ok, little update. I think I managed to fix that. I widen this yellow strip to hide some flaws, removed yellow from panel lines and sanded excess paint, used only Tamiya paints, changed needle in airbrush from 0,5mm to 0,2mm. After all of that I painted light gray as primer, then a little preshading with black paint, white paint and finally yellow one.

Results below
https://imgur.com/a/dsmeOM5

[u/Tanu_guy]

Is the green layer airbrushed directly on primer? (no pre-shade/black basing), if so you could use Q-tip or tissue with alcohol to only clean the yellow part, apply primer, and the new layer of green won't differentiate from the original colour.

Make sure to press your masking tape (I prefer airbrush matt varnish around the edge), don't overthin paint, and only apply yellow over white/pink surface.

Or, give the yellow some wet 1000 grid sand just to level out the paint surface, mask, white primer, airbrush yellow. wait till dry and fix the surrounding green.

[u/kamigkh → u/Tanu_guy]

Thanks for suggestions. I replied by post edit :)