There is no requirement for color, but if the color changes, it is not a registered trademark. This is unacceptable. You need to submit an application to change the color. When applied, the color of the specified color cannot be changed at will. If you change it, you have to apply again. If no color is specified, it is not needed.

the trademark law of the people's republic of china

Article 8 Any sign that can distinguish the commodities of natural persons, legal persons or other organizations from those of others, including words, figures, letters, numbers, three-dimensional signs, color combinations, sounds and combinations of the above elements, may apply for registration as a trademark.

Article 6 Where a registered trademark is required by laws and administrative regulations, an application for trademark registration must be made. Without approval and registration, it may not be sold in the market.

Article 24 Where the logo of a registered trademark needs to be changed, a new application for registration shall be filed.