Rainbow is caused by reflection, refraction and dispersion of white light. Therefore , what better color to use than white with VIBGYOR. I have similarly used white thread as the border for this rainbow band.

Step 1: Materials Required

White woolen thread 1.5 m long
Colored threads - 7 colors of the rainbow - 1.5 m long each
Scissors
Masking tape

Step 2: The Loop

Fix all the threads on a table with a masking tape at the center of the thread where you need the loop
Make sure the white thread is at the left most position as we need to use the white colored thread for the loop
The second picture shows the forward knot and fourth picture shows the backward knot
For the loop, you need to use a forward knot and a backward knot alternatively
Total we need around 10 forward-backward knots

Step 3: How to Start Your Band

Fix the loop part to the table with a masking tape
Make sure the threads are arranged in the order you want
Do a forward knot (f-knot) and a backward knot (b-knot) to secure the loop

Step 4: The Borders

I have used white color as the border so the white thread has to remain at the sides at all times
When you do a f-knot, the thread moves right and in a b-knot, the thread moves left
First start at the left hand side of your band...... do a f-knot with the white strand, which makes the white the second strand and the purple goes to the left side...... but we want the white to remain at the sides..... so do a b-knot which makes the white strand to go back to the left most
Follow the same with the RHS.... here do a b-knot first then a f-knot

Step 5: Row 1- Purple Row

Move the white threads to the sides
Start with the purple thread on the LHS..... Do a double f-knot with each of the threads till you finish with one red in the center
Now do from RHS...... do double b-knots with the purple thread till the center red
At this time you should have 2 purple threads in the center
Now do a f-knot and b-knot with the purple threads
Row 1 is done

Step 6: Row 2 - Indigo

Start with a f-knot and b-knot with the LHS white strand
Then do double f-knots with the indigo thread till the center purple
Then proceed to RHS...... b-knot and f-knot with the white thread then double b-knots with the indigo thread till you reach the center
When you have 2 indigo strands at the center, do a f-knot b-knot combination and row 2 is done

Step 7: Row 3 - Blue

Repeat

Step 8: Rows 4 - 7

One rainbow done

Step 9: Rows 8 Onwards

Do 3 more rainbows

Step 10: Finishing the Band

Finish it off with the white strand
You need to do double f-knots from LHS with the white thread till you reach the center and double b-knots from the RHS, center do a combo f-knot and b-knot and you are done!
Use all the threads and put a knot which will be pushed into the loop to secure on the hand
Trip the excess threads