A regular polygon with $$𝑛 \geq 5$$ vertices is said to be colourful if it is possible to colour the vertices using at most $$6$$ colours such that each vertex is coloured with exactly one colour, and such that any $$5$$ consecutive vertices have different colours. Find the largest number $$𝑛$$ for which a regular polygon with $$𝑛$$ vertices is not colourful.