Of course not. You can be photoreal. Just stick with black and white photoreal. nyuk nyuk.
I would consider it to be a major impediment if your ability to assess color is nil - but most men have color sense with some weaknesses - I am weak with certain dusky purples - sissy colors - so I consult the missus when I work with purple. That weakness is shared by 20% of adult males.
I worked with a color blind landscape architect. This was back in the days when we colored plans with those stinky markers. Squeak squeak, sssnnnniiiifffff, ahhhh. He learned his marker numbers and worked accordingly.
Partial color blindness doesn't mean you can't develop a reliable palette of colors, but it does indicate that you might miss an oversaturated green or whatever - a killer for any image. So have co-workers check you out.
With computer illustration, we have many years of experience in horrid ArchiCAD renderings from people allegedly not color blind but untrained in artistic image assessment. So there is more than one way to mess up besides by having a physical disability...
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If you are good at assessing tonal value, stick with toned monochromatic renderings. Figure out a good tint like sepia or ultramarine and illustrate in tinted greys. Most great renderings aren't accurately colored even if they are "photoreal." Besides, what IS reality, man?......
The computer doesn't render predictably out of the box. Every illustrator must tweak, and tweaking needs critical visual judgement.
Another barrier to success in rendering is that certain aptitudes suggest a lack of vision in other areas. For instance, when I was in design school, I felt that it was important to delineate with precision - my work was repressed. I met a woman who was in the associated interior design school and while we were becoming better acquainted, I noticed that she saw the world in planes of color and volumes of light and dark. Of course, school was meant to expand the mind and raise social standing. Now I think of space and color, and light and volume. To hell with making lines meet! That is a job for a servant!
Dwight Atkinson