Fix diagram and text for lack of color in print edition

ch09.asciidoc

@@ -193,7 +193,7 @@ To prove that a specific transaction is included in a block, a node only needs t
 .A merkle tree summarizing many data elements
 image::images/mbc2_0904.png["merkle_tree_large"]
 
-In <<merkle_tree_path>>, a node can prove that a transaction K is included in the block by producing a merkle path that is only four 32-byte hashes long (128 bytes total). The path consists of the four hashes (noted in blue in <<merkle_tree_path>>) H~L~, H~IJ~, H~MNOP~, and H~ABCDEFGH~. With those four hashes provided as an authentication path, any node can prove that H~K~ (noted in green in the diagram) is included in the merkle root by computing four additional pair-wise hashes H~KL~, H~IJKL~, H~IJKLMNOP~, and the merkle tree root (outlined in a dotted line in the diagram).
+In <<merkle_tree_path>>, a node can prove that a transaction K is included in the block by producing a merkle path that is only four 32-byte hashes long (128 bytes total). The path consists of the four hashes (shown with a shaded background in <<merkle_tree_path>>) H~L~, H~IJ~, H~MNOP~, and H~ABCDEFGH~. With those four hashes provided as an authentication path, any node can prove that H~K~ (with a black background at the bottom of the diagram) is included in the merkle root by computing four additional pair-wise hashes H~KL~, H~IJKL~, H~IJKLMNOP~, and the merkle tree root (outlined in a dashed line in the diagram).
 
 [[merkle_tree_path]]
 .A merkle path used to prove inclusion of a data element