The texture format that is used in qopenxrgraphics_opengl.cpp for OpenGL swapchain is GL_RGBA8, but Qt Quick 3D renders its contents with tone mapping by default, so we need to request GL_SRGB8_ALPHA8_EXT instead.

    // List of supported color swapchain formats.
    constexpr int64_t supportedColorSwapchainFormats[] = {
        GL_RGBA8,
        GL_RGBA8_SNORM
    };

As a temporary solution to get correct colors tonemapping can be disabled:

XrView {
    environment: SceneEnvironment {
        tonemapMode: SceneEnvironment.TonemapModeNone
    }
}

I think the truly correct fix would be to select a linear texture format (GL_RGBA8) if tonemapping is off and select SRGB format (GL_SRGB8_ALPHA8) if tonemapping is enabled.

Interestingly, SRGB format is already used in qopenxrgraphics_opengles.cpp, but it seems desktop OpenGL didn't receive the same amount of love