In Buy Mode, you'll see the tools on a skinny left hand panel -- you have to be in an editable area like inside a hero's building.
On that panel is a Create a Style mode in the left hand UI, just open that style editor and if there is a pattern/texture/color you want to reuse, drag the squarish block of color/pattern from the sample (in the color wheel box) of another object. There is no dropper tool, so just drag from the color wheel of a different object or pattern/texture in your game.
Below the Create a Style icon there is also a rubber stamp... so if you made a custom bed for example, use the stamp to duplicate that bed. You can also add customized styles to your game so you can reuse them by adding them to the style folder on the top left in buy mode of a specific object.
Hope that helps! Have a blast with your replay; it's such a lovely game! :heart: