Flight of the Navigator is purely fictional. It was made up by the writers and filmmakers to bring an imaginative adventure to the screen. There's no real-life basis for it.
From the title 'two thanksgiving day gentlemen story', we can't be certain who these two gentlemen are exactly. However, we can infer that they are the central characters in a story set during Thanksgiving. They could be from different backgrounds, perhaps one is wealthy and the other poor. Or they could both be ordinary people with their own stories and reasons for being part of this Thanksgiving - themed story. They are the key figures around which the events of the story revolve.
Red makeup and gentlemen are common combinations in ancient sentences. Here are some examples:
A gentleman's elegance is wrapped in red makeup. "Ten Miles of Red Dress"
2. Red sleeves add fragrance to a gentleman's wine. Dream of the Red Chamber
3. Red Sleeves Topple the City, A Gentleman Under the Heavens. The Imperial Concubine
4. A gentleman dressed in white with red sleeves. Legend of the White Snake
5. Red makeup, plain face, gentleman, cool breeze. Dream of a Brothel
6. Red sleeves add fragrance to a gentleman's world. [Tianya Mingyue Saber]
7. Red sleeves, a gentleman with a smile. Hua Qian Gu
8. Red sleeves add fragrance to a gentleman like the wind. Fuyao
9. Red sleeves add fragrance to a gentleman's world. "Feng Qiuhuang"
10. A red sleeve adds fragrance to a gentleman's fallen flower. 'Chu Qiao's Biography'
I hope these examples can provide you with some inspiration!
I have no clear information on whether 'Gentlemen' is based on a true story. It could be completely fictional or have some loose ties to reality, but without official confirmation, it's difficult to tell.