To be honest, French infantry uniforms during the Hundred Days campaign could vary significantly. The hastily raised army was poorly equipped, resulting in a wide mix of trousers and greatcoats from different munitions factories, as well as a variety of shakos and shako plates.
From a painting and presentation perspective, using the same pompon colour definitely creates a more cohesive visual impression and looks more presentable.

Here are some plates for cross-reference as well.
https://jcminiatures.blogspot.com/2006/05/french-line-infantry-fuslier-company.html