[Bug] [A11Y] Low text contrast < 4.5:1 : orange text on light grey (tab bar)

[pylapp]

Original issue

https://github.com/Orange-OpenSource/ods-ios/issues/554

Description

Low text contrast < 4.5:1 : orange text on light grey (tab bar) -> orange from brand design is not accessible on white background, so it's worth on grey. Recommandation : do not use orange for text on light backgrounds. For mobile use, recommanded text contrast is 7:1

Need update of design specifications