Indicates colour, perhaps, to be used in flooring (9)
I believe the answer is:
flagstone
'used in flooring' is the definition.
'flagstone' can be an answer for 'flooring' (thesaurus). I'm not sure about the 'used in' bit.
'indicates colour perhaps' is the wordplay.
'indicates' becomes 'flags' (I can't justify this - if you can you should believe this answer much more).
'colour perhaps' becomes 'tone' (colour is a kind of tone).
'flags'+'tone'='FLAGSTONE'
'to be' acts as a link.
Can you help me to learn more?
(Other definitions for flagstone that I've seen before include "One walked on" , "Pavior made from Teflon gas" , "Paving slab" , "It'll lay (some say) at ground level" , "Fine-textured rock" .)