I'll play. Let's assume that you are correct that the sun now appears to be white, and fifty years ago, it appeared to be yellow. Also, assume that there is only one Sun. Why does the sun now look white?

The way that colors of light work is that white is not the absence of all colors, but the opposite. It is the presence of all colors. To cancel out a yellow color, you would need to add magenta, or equal amounts of red and blue.

So, if chemtrails were dispersing metallic fog that was purplish in color, it would cancel out the yellow hue of the sun, resulting in a white sun.

https://www.cabrillo.edu/~jmccullough/physics10/files/ch27_color.pdf

I propose a research experiment to settle this. Find color photos of a popular beach front tourist destination during the 1960s with the sun shinning in the sky. Search the internet and your personal collections. Then find, or recreate a new photo this year. Try to use similar camera equipment, avoid photoshop filters, and take the photo at the same time of day. Compare the color of the sun.