The symbols or colours that we can visualize with this exercise:

Just like with the Rainbow the 6 colours also start at the one border from violet, and on the other side end in that colour again, before we start and after we finished , we may think of  violet (the highest of colour-vibrations) in spiritual perspective. We may also visualize starting at the Crown Chakra : taking a block of Indigo light, placing it at the 6th.Chakra, continue downwards to earth for "grounding", and so on for the next chakras, descending one step every time.

So we may also, before starting and after finishing, visualize violet; this finds a parallel in the thought: "Seek first the Kingdom of God and Its Justice, and all else shall be given to you"; al the Universal Teachers have in one way or another taught this most important thought! Because we are here going from top to bottom, downward, we will go from Indigo (6th Chakra) to Red at the 1st. Chakra.The next exercise (2) goes from the bottom upwards: exactly the other way.