Sir Isaac Newton in his early physics experiments decided the colors of the rainbow were Red, Orange, Yellow, Green, Blue, Indigo and Violet. Many of us remember them as ROY G BIV. Are there only seven colors? Newton believed in numerology and thought special numbers governed all natural phenomena. Seven is a very special number. There are seven days in the week, seven openings in our head, seven seas, seven continents and many other important sevens. So, of course he found exactly seven colors. In reality, the rainbow colors merge gradually into one another. Our eyes sort them into groupings. How many colors are in the rainbow? Anywhere from three to, as many as, several thousand. It depends on who is counting and what they believe is there. Funny how what we expect to see is often what we see.
The color order of the rainbow, starts with red at the outer edge and moves through the colors to violet. The brightness and the width of the bands and colors may vary greatly in an instant of time while you watch a rainbow and are related to the size of the drops that form the bow. The colors at the base of a rainbow are different from those at the top. Most rainbows only contain red near the ground. It is very rare that red is seen at the top of the rainbow. The width of the bow measured from red to violet will be about four times as wide as the full moon.
The rainbow's colors are like people, I have never known two to be exactly alike. To really understand the colors of the rainbow study them closely when they appear and come to your own conclusions.
Occasional when the sun is shining very brightly and the rain clouds are very dark a second much fainter rainbow will be seen above the normal or primary rainbow. Its colors are the reverse of the primary. They start with red on the inside and move to violet on the outside. The width of this bow is about twice the width of the primary bow.
It must be a clear and bright day to see the secondary rainbow since it is at least a quarter as bright as the primary.
On extremely bright sunny days you may see several fainter, thinner rainbows below the violet inside the primary bow. These rainbows are greater than the number we expect to see, and are called supernumerary bows. They are sharpest where the rainbow is brightest, at its highest point and are seldom seen along the legs at the base of the rainbow. They are alternately colored in pastel pinks and greens. The supernumerary bow colors and the spacing between the bows relate to the size of the rain drops creating the rainbow. The smaller the drops the larger the spacing between these bows. They tend to change rapidly in intensity and width. Whenever people claim to have seen more than two rainbows they are usually describing supernumerary bows.
Sometimes there are also very faint supernumerary bows created for the secondary rainbow. These additional rainbows lie outside the outer edge of the secondary bow . They are rare and very faint and only appear in extremely bright sun light against a very dark sky.