Say you have a squad of X-wings and the wing leader have an R4 astromech ( Decrease the difficulty of your speed 1-2 basic maneuvers) while the wingmates have no or a different astromech.

If the wing leader would reveal a speed 2 hard turn (white on dial but turned blue for wingleader due to R4), would this count as a white or blue maneuver?

The rules state:

• Before it moves, a wingmate is treated as revealing the same dial as the wing leader’s dial.
• After it is placed in formation, a wingmate is treated as having fully executed the maneuver on the wing leader’s dial. This includes the speed, color, and bearing of the wing leader’s maneuver.

My interpretation is that this means that the wing leaders maneuvers would be blue as well, but I am not 100% certain of that interpretation.

I assume you meant the wing mates maneuvers would be blue as well, not the wing leader.

I don’t think that’s correct. There is a question In the official ruling thread about whether these upgrades affect the revealed dial. This excerpt seems pretty definitive.

“ Note that abilities that alter a maneuver without causing the ship to select a new maneuver on its dial do not affect the ship's "revealed maneuver" as referenced by abilities such as Ric Olié's pilot ability.”

I believe a change in difficulty is passed to wing mates, but the reveal is, as you said above, for things like ric olié and dineé something something.

I'm with @Gberezowsky here. I wished it was the other way, because that would make things like Ello Asty sweet. Unfortunately, wingmates care about what's on the Leader's dial, not about the wing Leader's executed maneuver. This is consistent with how things like Cova Nell work: her ability works with R4 Astro or Leia because it only cares about what the dial says, not about what color the maneuver was while she was executing it.

So, to answer your question, R4 on a Wing Leader is not like getting a free R4 on everyone. It would be one color for the leader, and a different color for the mates.