A B C
1 USER REL 1 REL 2
2 red green blue
3 yellow blue
4 blue red
5 green red yellow

Hi everybody!
Hope an expert can help me. I'm really stucked and this thing is too much for me.
I need a formula that would allow me to verify the correctness of the table above.
I'll explain:

- The colors in columns B and C (REL REL 1 and REL 2) are always present in column A (USER)

- We see that in row 2 the USER "red" is related to "green" and "blue" (REL REL 1 and REL 2)
- In line 5 USER "green" is related to "red" and "yellow."

then:
- If the '"red" is related to "green", then the user "green" MUST be related to "red".

In some cases the condition may not occur and it would be required this bi-directional relation was re-established.

An example
- In line 3, USER "yellow" is related to "blue"
- In line 4, USER "blue" is related to "red" but not with "YELLOW". In this case, the cell C4 the formula should automatically write "yellow".

Another brief example:
If the USER "red" is related to "blue", then even the USER "blue" MUST be in relationship with "red", and if it is not, the system must complete the table.

I hope someone can help me. I really can't imagine how to solve this problem.
Thank you.

Aolo