You're seeing a common optical illusion, not a rendering error. Even if the color value is the same, font size makes it look different because of:

Anti-aliasing: For smaller text, your computer blends the text color with the background to smooth jagged edges. This makes the color appear less vibrant or even slightly different. Contrast: Bigger text creates a sharper edge against the background, making the color seem more "pure" or intense. How your eyes work: Our eyes perceive small details and colors differently. For tiny text, it's harder for your eyes to distinguish the exact color, leading to a perceived shift. It's all about how your brain interprets what your eyes see!