In Minecraft 1.15 Selection Icons Changed From A Blue Button To A White Outline, The Minecraft Server Selection Icon & The Minecraft Resource Pack Selection Icons Are Still Blue In 1.15.2, This Should Be A White Outline.
(This Screenshot is made while I was making a resource pack, this is not a texture I made)
Edit: I discoverd more icons that are not changed in 1.15.2: World Selection Icon and some buttons in the recipe book.