Colouring (2)

Here you will find that the chain will have two cell with the same colour in the same row/column/Block. That state is thus not possible.

All numbers of that specific colour can be eliminated. Marked with BROWN

See RED YELLOW chain with Yellow On Yellow in Row(3)

Look : It also have a colouring (1) in Row(1) Column(6)

There are four chains that the program will follow 1 2  :  3 4  :  5 6  :  7 8