Stool

I am being investigated for Kidney issues, and blood on my stool amongst other things.  As well as other symptoms, I have varying stool changes,[shape] 'flat' 'pencil' [colour].  Last week I had what appearded to be an emerald green stool, maybe blue in places, I'm not sure, but **I think** I can put that down to fresh blackberry juice [I drank the whole carton, as I do], however, I have of late at other times experianced green and almost yellow stools.  Yesterday, I had a hard lumpy stool, very creamy/pale 'clay'like in colour.
The colour changes don't last... they usually go back to the brown colour within 24/48 hrs.
Given that they go back to brown... could this still be a sign of some sort of liver problems?