There are many benefits to choosing and using artist paints that contain only one pigment, are pre-mixed and are referred to as 'hues'.  You can gain accuracy, save time and most importantly - money.

Single Pigment Artist Paints
The best results in painting come from use of colors based on just one pigment, as opposed to a mixture of multiple ingredients or pigments. A single-pigment color will mix truer and more predictably, and will give the benefit of maximum chromatic intensity possible for that pigment.

A dilemma that many an artist suffers is overworking a piece.  It can be hard to know when to stop and move on to the next piece or to scrape down and start over with the current one.

Have a plan. It makes little sense to attack your painting without some sort of process in place. Creating preliminary sketches and studies (smaller versions of the painting) will help you work through a number of the pictorial issues in advance at a much smaller scale and within a controlled number of variables.  This will make it easier for you to create the finished larger piece without spending precious time working on problems that may have been solved at a much earlier and smaller stage.