Choosing a paint colour to go with blue carpet is a matter of personal taste, but there are techniques to narrow down your options. The particular shade or shades of blue in your carpet can help determine the colour you choose for your walls and trim. The small colour cards from the paint store—known as swatches or paint chips—will help you determine the best colour to use for your own situation. Be sure to look at the various options under different lighting conditions so you have a better sense of how your new colour combination will look throughout the day.
Determine the tone or mood you want the room to have. For a vibrant look, such as in a living room, choose colours that contrast with blue such as gold or peach tones. For a classier look, such as in a home office or master bedroom, go for neutral greys, creamy whites or tans with slight orange undertones, especially with darker blue carpets. For a seaside feel, choose a lighter blue to set off the blue carpet, then a mid-tone blue or blue-green for the trim. For a dramatic look, contrast burgundy walls with dark blue trim and carpeting, or create a Victorian feel with lavender walls and mauve or pink trim.
Select several colour swatches from the colour range you've determined you want for your room. Also pick a few colours you simply like, even if you think they won't go with the carpet; you may find that they do.
Cut any white space off the swatches. If multiple colours are on the same swatch card, cut them apart.
Lay one paint swatch on your carpet at a time and look at how the colours interact. If possible, look at the swatch under daylight conditions, and then close the curtains and look at it under artificial lighting. Weed out the colours you don't like, and narrow the selection down to two or three potential wall colours.
Set the colours you've chosen on the carpet in different parts of the room so you can't see the others when looking at any one of them.
Lay a swatch of a possible trim colour next to each potential wall colour, and see how they look. Rotate each potential trim colour through all of the wall colours until you have settled on a combination you like.
Protect your blue carpet from the paint by tucking masking tape under the trim around all edges of the room and taping dust sheets down to cover the entire expanse of carpeting. Paint any ceilings first and then the walls. Paint the trim last.