How do you automatically fill cells with a specific word depending on the cells colour?

It's easy to do manually if (as I suspect) all coloured cells are in one column.
Select this column (or whole table), apply autofilter, use Filter by colour. select all visible cells (red) and in formula bar write 'chair" and press Ctrl+Enter
remove filter and you will see "chair' added only to the cels which were selected by filtering.

To do it fully automatically: will be not as easy as CF.
Especially if conditional formatting behaviour is to be reflected (you fill new cell with red, and there automatically appears 'chair' in it).
But even if you want to use some command: OK, now search the worksheet and put 'chair' in all red cells - it will require some coding (macro).