Let \(A=\{1,2,3,4,5,6,7\}\). We purpose to color all the subsets of \(A\) which contains 3 elements so that the condition below is taken into consideration:

"Every pair of non-intersecting subsets has different colours"

**Clarification**: If **B** and **C** are disjoint subsets of **A**, then **B** has a different colour from **C**.

What is the least possible number of colours to do that?

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