They resemble clear, dark grey strips of crepe paper lined up row after row with about the same amount of open space between the strips as the strips are wide. When the event begins, they appear to simply be lying on the ground. As the event progresses, however, they appear to move toward you, undulating over the ground, following the contours of the ground that they appear to move over. It can be a rather frightening experience, even if you know what is happening. Your body may want to run and hide, anyway.
Indigo is more difficult to distinguish from the blue and violet, however.
Interesting things happen when you are exposed to monochromatic light. In green light, red turns to the grey scale. Red clothing looks black or dark grey. There are a lot of myths about the danger of solar eclipses. Although it IS dangerous for you to look directly at the sun at any time, glancing at an eclipse would pose less danger in that a portion of the sun's rays are blocked.