You probably don't need all those colors dude! Your eyes won't even notice them when it's zoomed out. Some contrast makes it look better anyway! :-)

Same..
Our brain has a quality to abstract somethings, add anothers.. and in the whole art technique use this facts to fake the real world, a example is the dithering which you create a ilusion of a new color where it doesnt exist..
A good way to see these things it's by practice and studying/copying who knows well

But you doing well, keep practicing :]