Okay, so, I took a look at some Sonic Mania sprites and your colours are absolutely moving in the right direction. The heightened contrast is working, all i can recommend colourwise it to bring heavier shadows in and a quite bright highlight in order to give the same kind of contrast the rest of the game has. If you look at the sonic sprites, there are large sections of shadow, which serve to make the highlights pop more. Again though, going the right direction with this.
The main issue here is structure and readability. I would try and reform the sprite, taking into considerations the limitations of the games the sprites were based on. Try to tell us more with less i suppose. So, for the head shaping look at knuckles, dont define every spine, make into into one object which can tell us there are multiple spines there. Bring the hands down to the sides and perhaps take inspiration from amys idle from sonic advance. If the sprite is slightly more spread out we can read the character better. A good rule of thumb is that if the character was completely blacked out, could you tell which part was which or would it be a black blob? This is important as it helps us recognise the character faster.
I would also make the feet less round, Tikal has more... Trapezoid like feet? So try to form them that way more. Break her down into the simplest shapes and then convert that into sprite form. I have done it very basically here to give you an idea of what i mean(note:this is a ten second mspaint job, i'm sure you can do better than this):
Hopefully this has helped a little and if i havent been clear, let me know and i'll try to elaborate