Coloring By Number: Interior Designer is a color-by-number game that features a renovation theme. The player renovates rooms at various locations by painting images of furniture and other objects using paint-by-number tools and rules. They collect coins hidden within each image as well.
The locations include a studio, an apartment, an office, a house and a mansion. The game displays each one as a room with walls cut out to reveal the interior. The player can't access a locked room until they've completed the renovation at the last location. They choose a grayscale pixelated image of an object to start. They can paint the first one for free. They must use in-game coins to pay for access to the rest.
The player receives round-cornered square paint swatches on a palette below the field. To paint, they select a color and then apply it to pixels marked with the same number. After they use a swatch, it displays the amount of that specific color still needed during gameplay. The player reveals coins when they paint some pixels. When they finish coloring, the game then transfers the object to the room.
Coloring By Number: Interior Designer provides five free cherry bomb boosters and five free paint can boosters near the lower-right corner to help make painting easier. The bombs apply different colors of paint in a round blast area. Paint cans color all pixels that match a chosen paint swatch with one move.