Here’s an instance of a successful Red-Green alliance

Results of the French parliamentary elections today will set a strong precedent for the left going forward.

https://www.nytimes.com/live/2022/06/19/world/france-parliamentary-elections-results

In a serious blow to President Emmanuel Macron of France, his centrist coalition was projected to lose its majority in the lower house of Parliament. For the first time in 20 years, a newly elected president appeared to have failed to muster an absolute majority. The alliance of left-wing parties, known as the Nouvelle Union Populaire Écologique et Sociale (NUPES, New Ecological and Social Popular Union), led by the leftist veteran Jean-Luc Mélenchon, was expected to win 150 to 190 seats. The alliance includes France Unbowed, Mr. Mélenchon’s party, as well as the Socialists, Greens and Communists. Their vote was not enough to seize control of the National Assembly and force Mr. Macron to appoint Mr. Mélenchon prime minister, but it was a strong showing. Mr. Mélenchon, in a speech on Sunday to cheering supporters in Paris, called the results “absolutely amazing.” The alliance he brought together will be the main opposition force in the National Assembly.