Free French uniforms during WWII were quite varied - standardization was always a challenge as the source of the uniforms was a mix of whatever remnants of French issue they could retain, mixed with the supply they received from their allies (much of the campaign in North Africa they were supplied with British uniforms, then transitioned to US-supplied uniforms).
As for the Foreign Legion, the blue coats were pre-WWI. During the Great War, when the main French army changed to horizon bleu (approx. 1915), the Armee d'Afrique (including the Legion) got khaki uniforms, and that was the main issue right through to the beginning of WWII. According to Wikipedia,
https://en.wikipedia.org/wiki/French_Foreign_Legion , some remaining pre-war blue coats were issued in 1919 but it's likely that those stocks would be long gone by the start of WWII.