I'm just beginning to learn programming, but I have some knowledge about design and wanted to ask about design in particular. Is it important to have a certain color theme? I mean which color and shapes would be the best for a game design? In psychologty, we call it "color and shape eye" (concept from the research paper Psychology of colors and shapes on hireessaywriter.org).
Blue is the most pleasant, but I'm not sure if it's ok for a game. It's too dull.
Clair - Twitter - ClairrayRay

I'm not sure why this is a programming question - it's really a combination of aesthetics and ergonomics.
But in terms of programming the important thing is not to hard-code any colours. Make them some kind of global shared resource (details depend on programming language) and set or load the values at start-up time. This will also allow you to support multiple color themes, eg day and night. And it allows you to complete coding without any colour decisions, then try different colour pallets in the actual game to see which work best.

In terms of game design, you can apply the same psychology concepts in games. :) Only take into consideration the target audience, colorblind players, the theme and setting, hardware, and displays.

Now, on the technical and aesthetics side, it is ideal to keep a palette and be consistent with colors. Like the other response said, not hardcoding these colors is a good idea --you can do this in many ways, and depending on the engine and the assets you're using, but overall, just keep the color/palette definitions in a centralized place you can just update and from there apply to the rest of the game, ideally. It is easier to maintain this way, and this consistency will also be more visually pleasing to the players.