Perhaps the most important painter who didn’t show his work at the First Impressionist Exhibition in 1874 was Camille Corot, the most influential artist over Impressionism at the time. Several of the painters whose landscapes were hung on the walls of the empty studio in Paris were following in Corot’s brushstrokes.
Among them was Gustave-Henri Colin (1828-1910), who came from Arras, near Calais on the north coast of France. He trained locally at first, then with Ary Scheffer and Thomas Couture in Paris, but was most greatly influenced by Corot. His first painting to be exhibited at the Salon was accepted in 1857, following which he set his studio up near Biarritz, at the southern, Basque end of the coast of the Bay of Biscay.
There he painted landscapes en plein air, particularly coastal scenes. He also painted genre scenes of local sports including pelota and bullfighting. He met Whistler in 1862, and the following year his work was included in the Salon des Refusés. He shared a patron with Cals, Manet and Corot in Count Doria, whom he visited at the Château d’Orrouy in Picardy.

Many of Colin’s landscapes and other paintings showed the Basque region on the border between France and Spain, including his A Game of Pelota under the Walls of Hondarribia (1863). The game shown appears to be the traditional team version of Basque pelota, and this work, though bright and colourful, remains quite realist in its style. Hondarribia is a coastal town just inside the Spanish border.

Probably painted at about the same time, The Picador with the Bull (date not known) has looser brushwork and a more Impressionist look to it.

His more traditional Basque Country (date not known) shows an idyllic view of farming and rural life at the time, more Pissarro than Millet in its treatment.
At the First Impressionist Exhibition, the catalogue records that he showed five paintings:
- Haurra-Maria
- The Charpentier House
- Pond with Moorhens
- Fish sellers of Hondarribia (Spain)
- Entrance of the Port of Pasaia (Spain)
I’ve been unable to find any images of his paintings that might merit those titles.
Colin didn’t exhibit again at any of the subsequent Impressionist exhibitions, but continued at the Salon, where he was awarded a medal of honour in 1880, going on to a silver medal at the Exposition Universelle of 1889.

Judging from his appearance in his undated The Painter in his Studio, this was painted well after the First Impressionist Exhibition.

The Garden House (1894) is a late work suggesting little change in style even into the final years of the century. He was appointed to the Legion of Honour, and died in Paris in 1910.
Gustave Colin was perhaps unfortunate in not staying near Paris to paint, and when the avant garde moved south to the Midi, he had based himself too far to the west. Such are the vagaries of fashion in art.
References:
Hans Weevers’ page with a thorough literature survey.
The First Impressionist Exhibition (in Italian), containing
the exhibition catalogue