How to change speaker for sound?
Game boy color purple clear. 1998
Here’s a link to the ifixit Game Boy Color 主板更换 guide.
It shows how to remove the motherboard so that access to the speaker is possible. You will need soldering skills and tools to carry out the repair.
Here’s an image taken from Step.7 in the guide showing the location of the speaker (highlighted)
(click on image to enlarge for better viewing).
Replacement speakers are available online from places such as Ebay etc.
Here’s a link to just one supplier. It is only shown to give you an idea of the cost of the part. There are other suppliers that may suit you better.