Do people with raynaud's always have blue fingernails?

No . Only with nail polish! the fingers and nails may go through the red, white and blue cycle. Sometimes we miss it!
No. People with raynauds can see color changes when exposed to cold or emotional stress. The blood vessels in the hands and feet go into spasm causing decreased blood flow and oxygen to those areas. First they turn white, then blue and finally red when the blood flow is restored to the areas. The spasm is temporary and eventually the color returns to normal.