You might be confused because Font Color isn't a text-based option like the others.
If you're using FCP's default Text tool, click on the white square to the right of Font Color.
If you're using Title 3D, which gives you more options (such as built-in drop shadow, outline and multiple fonts and sizes in the same card), click on the area that reads "Title 3D - Click for Options", select the text in the upper area, then go into the third menu below to change the colour. Title 3D
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