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I took a closer look and saw that you're attempting to shade the font. The colours are still too close together (in lightness value, try to get 20+ difference between your colours, so if you have 100, use 80, then 60, this works well in my experience for low colour count spriting) and if you want to hue shade, try to get 15+ difference in the hue value, towards blue/purple for darker and towards yellow for lighter.
The shading is darker from the outside of the logo with the insides of the logo being the lightest- this implies that the light source is between the logo. Try to think about where the light is coming from, if it's above, does the 'U' block the light?
The colours could use less saturation also. The green and orange are too vibrant, my first thought was of a late 80s logo I saw on a VHS tape case once.
I like the logo as a whole, my only feedback would be to introduce a beige or grey to shade the edges of the logo.