The color of paint and total coordination are important to make look bigger and beautiful for your house.
For the color, more white/beige/off white will show the room bigger. And, It is better to choose a bright color to the ceiling. The ceiling is able to see like as high.
And, If you would like to choose a dark color and you want to show bigger, it need the wall molding with bright color, and it will be the beautiful and gorgeous design. However, it is better to choose the bright colors if you want to make your house look bigger more.
And, If you would like to consider the total coordination, It is better not to change the color in each room. Although many people will change the color in each room, the house will be visible cheap. However, designers will consider at the same time the design of outside and inside the house.
For example, outside of a house is classic, but the inside house is kindergarten. Some house has given the impression like this, actually. Many person chooses a lot of colors because the printing cost is usually same. However, the house looks a cheap.
It is very important that you match the color of the whole house. Please try to reduce the kind of color you want to paint. And please choose a similar color. You can get the beautiful house renovation in harmony without having to hire an interior designer.
And, if you want to use lots of colors and consider beauty and design, it needs a very good skill that is an expert. Most interior designers can not coordinate it. You need to hire a specialist for color coordination. (We have a lot of the interior designers, However, the interior designer who can harmonize a lot of color is only one person.)
For the paint cost, it usually does not charge extra even if you want to paint a lot of color. (But if you want a lot and a lot of color, the cost will be high. But usually nobody request so many colors, So it is no need extra cost for paint.)
It is to choose a bright color paint to make your house look bigger. And, it is to harmonize the color of the whole house in order to look beautiful. A simple tip is to reduce the kind of color you want to paint. However, if you want to paint a lot of color, It is necessary to hire a designer with an excellent color sense even among interior designers. If you need our help, please ask us.
I think light colors are perfect if your house is small. These colors makes your room look bigger.
I also agree with you. light colors are perfect for the small house. However, some person want to make looks bigger house but they want to choose a dark color. It requires the know-how of interior design and renovation.