Colours in stone (4)
I believe the answer is:
flag
I believe this is a double definition.
'colours' is the first definition.
(colour can mean a national flag)
'stone' is the second definition.
(flag is a kind of stone)
'in' is the link.
(Other definitions for flag that I've seen before include "Iris - paving slab" , "Emblematic rectangular piece of fabric" , "Colours - become tired" , "Languish, decline" , "Jack, for one" .)