I have had the following Johnnie Walker expressions:
Red: swill not suitable to mix. Seriously, pour it down the drain.
Black: decent to mix, or serve in tumblers over ice to non-enthusiasts. Nothing I want to drink. On par with Chivas.
Green: a very nice dram, with the boldest flavors in the JW lineup. Tasty! A bit of spice.
Gold: more subdued than the Green, but with the same 'island' profile. Very smooth.
Blue: incredibly smooth, hints of...everything. Very well balanced. Easily approachable, even for someone who has never tasted whisky.
I would (and have) buy JW Green for my cabinet. It is worth it's price of $50 or so. I can't seem to find Gold for less than $90. For that, I could have HP18, Auchen Three Wood, or Bunnahabhain 18. No thanks.