Welcome to the forum.
Looks like you have a 1985 or 86 Gitane Performance frame. The decals are 1984 style so it may have been the beginning of the model run.
1984 decals
1985-86 decals
Columbus Aelle was their 2nd tier tubing made of manganese alloy steel. It was heavier than their top of the line SL chrome molybdenum alloy steel tubing from that era. Frames made of Aelle tubes were 10 to 15 ounces heavier than SL tubes depending on frame size. (less than a pound)
The geometry chart in the 1985-86 US Gitane catalog shows dimensions for a 54cm size frame.
The 1984 catalog shows dimensions for a 57cm frame - your frame is similar to the Criterium model.
Your frame looks like a 57cm or 58cm size so the 1984 dimensions would apply.
I have a "full house" of the top four 1984 Gitane models: Criterium, Tour de France, Super Corsa and Team Professional plus a 1985-86 Professional.
They're near the top of the list of my all time favorite riding and handling bikes.
Serial number??? Save it for the Loto!
There's no records, traceability or logic used by many French bike manufacturers.
As to the color??? It's a frame made for the European market. They offered a wider selection of colors. Trek imported Gitanes for a few years in the early 1980's. They only offered 1 color for each model.
The headset and BB have inch size threads while the tubes are metric. It will probably take a 26.4mm or maybe a 26.2mm seatpost and a 22.2mm stem.
Enjoy!
Chas.
SF Bay Area, CA USA
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1984 Criterium
1969 TdF
1971 TdF
1974 TdF
1984 TdF x 2 Bikes
1970 SC
1971 SC
1972 SC
1984 SC
1984 Team Pro
1985 Professional
1990s Team Replica