Custom Mario Sprites

[Vipershark]

Are the colours better?

Better? Yes. Correct? No.
You did no hue shifting or changes in saturation at all and just lowered the brightness on each shade.
The contrast is better than it was, but you still need more.

I'll make a crosspost from another thread that I posted about hueshifting in.

Let's take your red gem as an example.

Look at the color picker in paint. What you've done is simply move the color selector up and down, but you haven't changed your hue at all. For each of your shades, the hue is still zero, which is a flat red.
What you need to do, in addition to changing saturation (up and down on the color picker) and brightness (up and down on the slider), is move left and right on the color picker to change your hue as well.

Darker shades hue shift to cooler colors, while brighter shades hue shift to warmer colors.
In the case of red, you can hueshift down to, say, the purple region for dark shades, while your light shades can hueshift up as high as orange or yellow.

You need to use all three axes of movement (left/right, up/down on hue/saturation grid plus up/down on brightness slider) to pick colors that work well, not just one or two.

I guess the easiest way to describe it is that you almost want to be moving diagonally on the grid to pick the general area for each shade and then using the brightness slider for fine tuning, but every palette is different so that might not always apply.

To adapt this to your case, all you did is move the little slider (the brightness slider) on the right side of the color picker to a darker brightness level each shade, but you didn't move around the color grid.
You have to use hue shifting (left and right on the grid) and changes in saturation (up and down on the grid), too.

Maybe I should try to do some sort of a tutorial video to show the basic idea behind correctly choosing colors.
Would that be helpful?