This article will show you how to change the background color in Adobe Illustrator.
Steps

Step 1. Open the image in Adobe Illustrator
To do this, double-click the yellow “Ai” icon, then click File> Open from the menu bar (at the top of the screen). Select the image whose background color you want to change, and then click Open.

Step 2. Click File on the menu bar

Step 3. Click on Document Options
It's near the bottom of the drop-down menu.

Step 4. Check the box next to Simulate colored paper
It's in the Transparency Options section.

Step 5. Click on the upper window with a color sample
It's on the right side of the Transparency Options section (to the left of the mesh image).

Step 6. Choose a background color
To do this, click on the desired color on the palette, and then adjust its saturation using the slider.
When you're done, the selected color will be displayed in the swatch box in the lower left corner of the dialog box

Step 7. Click on the swatch and drag it to the empty square
The empty squares to the right of the color swatch allow you to save custom colors.

Step 8. Close the dialog box
On Windows, click X, and on Mac OS X, click the red circle in the corner of the dialog box.

Step 9. Click on the lower box with a color sample
It's on the right side of the Transparency Options section (to the left of the mesh image).

Step 10. Click on the color you just saved
You will find it in the small square at the bottom right of the dialog box (in the square where you dragged the color you want). The swatch window (in the lower left corner of the dialog box) displays the same color as the small square.

Step 11. Close the dialog box
On Windows, click X, and on Mac OS X, click the red circle in the corner of the dialog box. The color swatches and the grid will display the color you want.

Step 12. Click OK to close the Document Options dialog box

Step 13. Click View on the menu bar

Step 14. Click Show Transparency Grid
It's near the bottom of the drop-down menu. The background color will change to the color of your choice.