If you are using a Prusa XL to print:

Import both STLs together and select "yes" when prusaslicer ask if it should be imported as one object with multiple parts. 

Scale to your desired size, I scaled mine to 100mm x 100mm x 5mm

Use the object parts to assign different print heads with your desired color. 

If you are using a single extruder printer, I assume you might want to use the paint functionality to assign your preferred colors. Remember to scale the print as needed.

I printed it in eSun Cold White and eSun Red

I printed with 2 perimeters and 15% infill but you can adjust this as you see fit.