So please don't judge me; this has been bugging me for a long time, and I just want to be able to forget about it.

I saw this movie in July or August 1986. It wasn't a commercial movie - I didn't see it in a normal movie theatre.

The story takes place somewhere there are 3 nations, each on its own cloud. The yellow nation, where the story's hero is from is modern and everything is yellow. There are overtones of a police state here. The hero is some kind of tinkerer/inventor and creates a large hoop that enables him to fly. (Picture Vitruvian Man where the circle is a yellow hoop, except he's wearing a yellow jumpsuit.)

The hero flies to the red nation, which is more overtly militaristic. Here the hero encounters a young woman dressed entirely in red. Guards (in red) chase him off, but she gives him a red rose. She is taken to her father, who seems to be the generalissimo in charge. The architecture of the red nation is brutalist; large blank slabs. I remember large square plinths, but I may be conflating memories of Golgorath.

Meanwhile, people have been watching our hero fly through a telescope in the blue nation. The blue nation is very Louis XIV, aristocrats and courtiers with lots of blue lace.

The hero returns to the yellow nation where he is immediately arrested and dragged before the ruler (queen?). He presents her with the rose and she glares at it until someone douses it with yellow paint, at which point she picks it up and smiles. Nastily.

The hero is put to work building more flying hoops. Some time later, troops of yellow painters (yellow coveralls, yellow power-rollers, yellow backpacks full of paint...) are sent flying to the red nation. At the same time a huge (blue) hot-air balloon takes flight from the blue nation, and they converge on the red nation.

The yellow and blue contingents start painting the red nation, which fights back with a huge machine that I recall looking like a gigantic (red) fireplug. Of course blue paint meets red paint, red paint meets yellow paint, yellow paint meets blue paint, and everyone marvels at the new colours.

I seem to remember a title like "Color Wars" but that's not helping me find it.

I know, dumb right? But it bugs me.

Rainbow War (1985)

Summary

Rainbow War was featured as part of Expo 86 in Vancouver, BC, Canada.

Three nations with strong ideological differences go to war when new technology brings them into contact with each other. Blue King, Red King, and Yellow Queen:

Not everyone finds their differences repulsive. Yellow Boy and Red Princess:

The three sides in the battle discover that their differences can combine in beneficial ways and that they have much to gain by working together, which leads to peace:

Various scenes

The hero is some kind of tinkerer/inventor and creates a large hoop that enables him to fly. (Picture Vitruvian Man where the circle is a yellow hoop, except he's wearing a yellow jumpsuit.)

The hero returns to the yellow nation where he is immediately arrested and dragged before the ruler (queen?). He presents her with the rose and she glares at it until someone douses it with yellow paint, at which point she picks it up and smiles. Nastily.

The hero is put to work building more flying hoops. Some time later, troops of yellow painters (yellow coveralls, yellow power-rollers, yellow backpacks full of paint...) are sent flying to the red nation. At the same time a huge (blue) hot-air balloon takes flight from the blue nation, and they converge on the red nation.

The yellow and blue contingents start painting the red nation, which fights back with a huge machine that I recall looking like a gigantic (red) fireplug.

Seems like it is Rainbow War.

From Wikipedia:

The story takes place somewhere there are 3 nations, each on its own cloud.

Once upon a time, in a timeless place, there were three kingdoms: one blue, one red, and one gold.

The hero is some kind of tinkerer/inventor and creates a large hoop that enables him to fly.

In the Golden kingdom, a young boy creates a flying golden ring, large enough to carry a man. Using it, he leaves the Golden kingdom to explore the other lands.

The hero encounters a young woman dressed entirely in red. Guards (in red) chase him off, but she gives him a red rose.

The Yellow boy lands in the Red kingdom, and falls in love with the
Red princess, and she with him. He gives her his golden scarf, and in
return, she gives him a red flower.

The hero returns to the yellow nation where he is immediately arrested and dragged before the ruler (queen?). He presents her with the rose and she glares at it until someone douses it with yellow paint, at which point she picks it up and smiles. Nastily.

Upon arriving, the Yellow queen hails him as a hero. But when he
offers the red flower to her, she is offended, and the Yellow guards
take the boy away. The Yellow queen then realizes that with the golden
rings the boy has created, she can invade the other kingdoms.

The yellow and blue contingents start painting the red nation, which fights back with a huge machine that I recall looking like a gigantic (red) fireplug. Of course blue paint meets red paint, red paint meets yellow paint, yellow paint meets blue paint, and everyone marvels at the new colours.

Meanwhile, in the Golden Kingdom, the Yellow boy is being forced to
make golden rings for the army. He manages to outsmart the slavemaster
though, and escapes. Back at the front, the battle is still going
colorful and strong. But when a volley of blue and yellow paint
collides, green is created, and the soldiers from both sides stop
fighting, very interested and happy at what they have created. The
Golden queen will have none of it however, and commands her troops to
continue fighting. The battle resumes. The Red army, using a giant
fire hydrant, coats the whole area with red paint, and when it mixes
with the other paints on the field, they discover orange and purple,
and the soldiers from all sides again are entranced and overjoyed over
these new ideas.