I set some text in a label to color #FFFFFF, now it doesn’t match the others though.
I delete color and it still looks darker. I changed it to #555555 and #2b2b2b.
What is the default black color of text?
I think the position might be one of those positions and colors that just looks odd no matter what I do.
The default color is CSS variable and set by var(--label). You can see this if you enable your browser’s Developer Tools and inspect a label. The actual color will depend on the selected CSS theme in use on your project.
You should be using themes and preset CSS variables rather than direct formatting. That way you can switch themes and everything will work.