The FontColor property of uilabel affects the entire label.
There is no built-in method of coloring parts of labels.
As a workaround, you could contiguously position several labels containing parts of the full label and set the colors of each partial-label accordingly. You'd likely need to use a fixed width font to get the spacing right but even with a fixed width font, this will be tricky. To set the FontName to your systems default fixed width font see this answer.