Feedback for Custom Sprites

[NicoDGames58]

So, I'm working on a ROM hack of FireRed, and the first thing I'm working on is the art for the game. I'm starting with the outside areas tileset and I've just created a tree and grass texture. I'm not sure how good they are, so feedback and ways they could be improved would be appreciated, since I'm out of ideas on how to improve the textures. Also, there are probably really good tutorials out there for this sort of stuff, so if you know of any I'd really appreciate a link to it. Thanks.
Also, there should be around 7-8 colors in the tree texture and 3 colors in the grass texture. If you don't see them all I'd recommend changing your monitor's contrast settings since being able to see all the colors is obviously very important.
Tree:

Spoiler:

https://imgur.com/a/pFfJotZ

Grass:

Spoiler:

https://imgur.com/a/Sua68wF

 

[juliorain]

Be careful about color shifting! Hue shifting also translates color temperature! While shifting is ok for an art piece you should use it more selectively on tiles because of the amosphere it will create. For instance, right now, your bluer shadows suggest colder and confusing light. While I understand that shifting is used to soften the often boring value gradients, too much color shifting creates other problems. You'll also need to carry the shading back into the bottom outline of the tree which flattens it.

Your grass is unnaturally green. It's almost like the gen 5 spring grass on steroids. We're making use of a similar hue only because it is an unnatural green. I think you can play around with the hue just a little but.

Also I recommend wrapping the

 

[NicoDGames58]

First, thanks for your reply. I've changed up the color on my grass tile:

Spoiler:

. It should look less green. Also, I'm an art noob so I'm not really sure what you're trying to say about the tree texture and I don't really know what your trying to say when you say stuff like hue shift. Could you please elaborate on what you were trying to say so that I can understand the feedback you gave me?
Thx :)