First of all, I would be hesitant to embrace ideas that claimed their validity because they've been around since 1919. Just saying. IQ tests are not settled science, because there's no possible way to measure exactly how much environment, socio economic status, nutrition, and test bias can affect the results. Thus, you find that there are two camps, neither with indisputable conclusions.
Also, a study of DNA ancestry by McGill University of Montreal shows that most African Americans have some European ancestry.
Since you have so many friends of color, and have observed the successes of others, I take it then, as long as they adhere to the customs, language, and culture of Western civilization, you have no problem with immigrants. So as long as that is a given, I see no problem with the population getting a little browner.
You ask, how do you determine race? Obviously, you define it as the color of individuals, going by your Frank Bruno example.
Your Gaelic example is laughable, because they would be considered white, it doesn't matter what their ethnic background is.
So, despite your protestations, most of those commenting here would prefer to live in an all white society. Just because they admit that there are some worthy, intelligent people of color, doesn't nullify their prejudice. It's too close to that old argument, "some of my best friends are black!".
Some here think I'm a weepy liberal, but I'm actually a liberal realist. There are two ways to look at the situation. Someone who prefers whites will complain "the world is getting browner!" You could equally claim the world is getting paler, if you come from Swaziland.
You will never convince me that someone who wants to live in an all white country doesn't consider whites to be generally superior to other races. It has nothing to do with "Western Civilization", no matter how you try to veil it with cherry picked examples of how whites are responsible for all major achievements. Whites had superior weapons, and forced their culture upon the rest of the world. When Europeans were floundering around in the Dark Ages, Arabia kept the flame of knowledge alive. It all boils down to that old adage. "to the victor belong the spoils."
Whether by force, or simple assimilation, there's no going back. I plan to make the most of the situation by enjoying all the new experiences and interesting people I come across. I doubt that it will harm me or my children. even if their children are darker than me.
So you see, I plan on having it both ways, being proud of my heritage, and sharing it with others, while learning and embracing the best of others.
"You may say I'm a dreamer, but I'm not the only one".