I mean all possible keys combination, just wonder if you can still get new, unique color on acoustic piano or - as they say: "since Bach, Mozart, Beethoven and few others everything was played already..."

I estimate that there are around 3.5 billion 10 note chords you can play. (80 * C(12,5) * 70 * C(12,5) -> 3,500,000,000)

So the answer to your question about strict "key combination" is definitely "no".

As far as "new, unique colors" though, there are two things to consider. On the one hand, many of these distinct chords are going to sound similar, and won't really provide new colors. I have no idea how to estimate how many distinct colors those 3.5 billion chords really contain; this question very quickly gets into psychology and the science of perception.

But on the other hand, just looking at chords is probably too reductionistic. I can group together chords that Beethoven used into a new sequence, and produce an overall "color" he never would have dreamed of. (Not that it would sound very good.) I think there are more colors than chords we can play, just as there are more literary voices than words in the dictionary.

-Jason

Colors are more about the relationships between chords than the actual build of the chords themselves. See Debussy: he could take diatonic chords and make you see them in a completely different light by using a technique called planing. So I think there will always be room for new colors.

That reminds me of the old kamasutra joke - the difference between position 112 and 113, your fingers are crossed.