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If by "words" you mean the labels of the functions then all you have to do is hit ctrl+a while on the block diagram and select the desired font color. This will update every label on the block diagram to have the font color you specify.
Using the select all method will also modify the font size and color of any "text" in a constant. It will not change the font size or color of the text on a local variable, and I don't know of any way to do this.