No but they should look better! Tintypes do not interpret colors the same way a black and white image would, as the process is least sensitive to light in the blue/UV spectrum.
Blues tend to appear almost white while reds appear very dark. Sometimes clothing and skin tones may appear different than expected due to the pigments that make up the colors. In general, freckles and wrinkles will look more pronounced and patterns and textures will have more contrast, while tattoos will disappear.