Do I have to register every colour variation and style variation of the design?

No, you do not need to register every colour or style variation of your design separately. When you register a design, it typically covers the overall visual appearance of the design as applied to the product, including its shape, configuration, pattern, or ornamentation. However, if the variations significantly alter the essential features or the overall visual impression of the design, separate registrations may be necessary to ensure full protection.