I have heard that the test of a good chef can be based on how well they can cook an egg. In the design world, the test of a good graphic designer is in their ability to create a great logo. If you've worked with a professional graphic designer to develop a logo, you may have noticed they always start with black and white. There two very practical reasons for this:
Reason 1: Versatility
A test of a good logo is it's versatility. Your logo may be your pride and joy - you've been using it for years and to you, it's better than sliced bread. However, if your logo is not versatile, it is not a good logo.
Think about it - your company logo is on every single thing you produce to represent your company. It will be printed on your business card and letterhead, on your brochures. It will be fabricated into a sign that sits outside your building and on the wall behind reception. It will be posted to your website, in 72dpi and probably no more than an inch or two in diameter. You may use it in black and white for newspaper advertising or on a fax sheet. You may even embroider your logo on caps and silk screen it on tshirts for the company softball team. If your logo has lots of tiny details, varied shades, or only works in color, you are in trouble.
Reason 2: Color is emotional
During development phase, it's essential to work in black and white. Color automatically incites emotion and that can seriously interfere with your perception of the design. You'd be surprised how much a color can sway your final decision. It could keep you from choosing the best option for your company simply because designer presented the idea to you in orange - and holy moly do you hate orange.
Now that's a good egg
If you are working with a professional designer, they will not make this mistake. They will create the logo in black and white and only move on to color after the black and white design has been approved. If you are not working with a professional, its up to you to make sure you logo works in black and white as well as it does in color. That's not just a good egg, it's eggs benedict.