Read about the issue in this stackoverflow question.
Still have the same issue after trying the solution. If I change the @”\u2714″ to @”\u2418″ the X is displayed in the requested color. The solution to not use system font didn’t work for me. After switching the font for the text label from System to Custom Helvetica Bold 21.0, the check mark still displays in black, not green.
Zapf Dingbats works.
I guess for some reason the heavy checkmark character was given an Emoji graphic, even though it doesn’t show up in the Emoji keyboard, and the system now uses that graphic for the character in every typeface that doesn’t have its own version. Zapf Dingbats was the only “font variation” in the Character Viewer that’s also one of the fonts on iOS.