Drawing and painting

I am taking a drawing class, again, to revisit values and technical techniques. I am taking it with a wonderful instructor who worked in the industrial arts industry for years. It is an excellent review of things I knew and forgot.
I am continuing with my oil painting classes,too. My bottle study is almost done. I learned why my paintings sometime go back to a "sweet" look. I am have a tendency in the 4th stage to use the same two colors. It is important to add several colors to keep them dull rather than go back to bright. This dull is so important in painting.