807.03(d) Changing From Special Form Elements to Standard Characters, or the Reverse, May be a Material Alteration
A special form drawing containing a design element, color, a claim to a particular style or size of lettering, or other distinctive elements cannot be amended to a standard character drawing, unless the examining attorney determines that the amendment is not material. 37 C.F.R. §2.72.
Conversely, a standard character drawing cannot be amended to a special form drawing containing a design element, color, or a claim to a distinctive style or size of lettering, unless the examining attorney determines that the amendment is not material. 37 C.F.R. §2.72. See TMEP §§807.14 et seq. regarding material alteration.