I applied a thin layer of oil paint and left the painting for some time. I've been using water mixable oil paints all the time. I had no problems with Lukas Berlin oils, which I've been using previously. This time I mixed in Cobra oils, which I've never used before. Also, I want to mention, that for this painting I didn't use any mediums, neither did I mixed colors with water. Before painting I applied two layers of gesso to the canvas.

After a couple of days, I noticed immediately that the color has shifted from light brown to greenish (see pictures below). At first I thought that different appearance is caused by changes in ambient light conditions, but changes are too noticeable. What is the cause for this and what could I do to prevent this from happening further on?

I applied a thin layer of oil paint and left the painting for some time. 
I've been using water-mixable oil paints all the time. I had no problems with Lukas Berlin oils, which I've been using previously. This time I mixed in Cobra oils, which I've never used before. Also, I want to mention, that for this painting I didn't use any mediums, neither did I mix colors with water. Before painting, I applied two layers of gesso to the canvas.

After a couple of days, I noticed immediately that the color had shifted from light brown to greenish (see pictures below). At first I thought that this different appearance is caused by changes in ambient light conditions, but the changes are too noticeable. What is the cause for this and what can I do to prevent this from happening further on?

I applied a thin layer of oil paint and left the painting for some time. After a couple of days, I noticed immediately that the color has shifted from light brown to greenish (see pictures below). At first I thought that different appearance is caused by changes in ambient light conditions, but changes are too noticeable. What is the cause for this and what could I do to prevent this from happening further on?  

I applied a thin layer of oil paint and left the painting for some time. I've been using water mixable oil paints all the time. I had no problems with Lukas Berlin oils, which I've been using previously. This time I mixed in Cobra oils, which I've never used before. Also, I want to mention, that for this painting I didn't use any mediums, neither did I mixed colors with water. Before painting I applied two layers of gesso to the canvas.

After a couple of days, I noticed immediately that the color has shifted from light brown to greenish (see pictures below). At first I thought that different appearance is caused by changes in ambient light conditions, but changes are too noticeable. What is the cause for this and what could I do to prevent this from happening further on?