Currently the game is a mix of a puzzle and an execution game. One the one hand the player needs to find the correct path and on the other hand he has to press the buttons to execute the path without stopping.
Maybe the game will benefit, if you make it a pure puzzle game. You could do that by replacing the smooth movement with grid-locked movement and replace the time counter with a step counter. So a level would be : "You can make 4 steps on green, 6 steps on red ...". As I said, the game will be much more puzzly then. Depends on your taste, if you like this more.
Besides that you can improve two small things:
- Instead of letting the player press Space to start, let the player just start. As soon as the player presses an arrow key, the timer should start
- The human eye is not very good at seeing absolute colors. I found it difficult to judge from the depleting color, how much time I have left on each of the color. Maybe you can try a Health-bar-like display for the time left in the three colors?