Lets note some key things about the original image.
The whale looks to be entirely blue in the original except for part of it's mouth which has gained a purple hue. The top of the whale's mouth is also curiously blue/dark purple fading to a pinker color as we move closer to the jaw of the whale.
The bricks are all very dark, with a sort of bloom style highlight. A key example of this, is the block above the furthest ring to the right. Here we can see the "face" of the block is rather dark. While the front of the block is quite bright. If we look where the face and the front meet we see a very sudden drop off and a slight glow.
Lets look at the grass in the original. Notice the dark almost playful way the artist used shadows to give us a sense of depth. The color in some of the blades are slightly different giving us a feeling of a more realistic undergrowth.
Sonic while poorly positioned in the image is given a much darker shade then what was used in the genesis titles, he also has true light shadows which causes sonic to be slightly too dark and has a slightly muted feel to him.
Now lets look at the first recolor.
The whale's mouth has been slightly corrected, though I feel the mouth still needs to be pinker towards the roof of its mouth. The whale itself has also undergone a slight color change becoming more purple overall, The purple hue seems a bit off. Not necessarily bad, just off.
Lets move on to the blocks, they have become much easier to distinguish compared to the original, the sudden drop offs in light values are not present in the recolor. However, the recolor also looses the slight tinge of green the original had. I feel as if the artist purposely put the green there to give us the feel of moss on them, the recolor loses this in favor of being more uniform and bright. The same effect is applied to the brick art in the recolor, though the green is not completely removed in the level art itself. However the original art had small cracks in the bricks this is a much less noticeable effect now.
The grass leaves in the recolor loose the entirely green look in favor of adding some yellow to the mix. This gives the entire scene a much brighter look to it, which is nice. However it also removes the playful shadows the original had. I personally like the addition of the yellow to some of the leaves but I feel they are perhaps a shade too bright.
Finally lets look at sonic in the recolor. He was drastically brighten compared to the original, this has a two pronged effect. First it makes sonic sharper and more "hard" compared to the "soft" and somewhat fuzzy look of the original. Secondly because of the way he was brightened he is much closer to the look of the original sonic, he also stands out in the scene much more now. He also loses the blue/green tint which seemed slightly out of place in the original.