The case of identical colors coming out way different

I bought 3 SW paint pots. I have painted them on white paper and they are 100% true to the color swatches and look great. I did a quick swipe with a paint brush on the old wall at my home (which has an off white color on it currently). The colors are coming out WAY different. My SW Sea Salt color is going from green to periwinkle blue and my amazing gray is going to purple brown. These are not just close changes, I am talking it looks like I chose to paint my room purple. I have spent countless hours picking out these samples to be this disapointed is unbelievable. I don't know what to do.

Colorman says:
I see two possible issues here:
1: The current color affects the new layer of paint. This can be solved by painting a second layer.
2: But more likely this is a case of metamerism. 
Meta what?
Metamerism means that colors perceived in a certain light will appear exactly the same to our eyes. But under another source of light, say an electric bulb, they will come out different. So if you change the light, two colors that first looked the same, may now appear different.

There's not that much you can do about metamerism. It's just a fact of life. However, you can deal with it by always evaluate your color under the same sort of lighting that you'll eventually use. Also, if you want to copy a certain color in your house in paint, most modern paintshops will be able to take metamerism into account. So if you take a sample of the color to the paintshop and have it measured there, metamerism shouldn't be an issue.