Welcome to the community. Sorry that you find the bass on your SoundLink Color II too overpowering. I'll do what I can to help.
There are no adjustable tone controls on your SoundLink, but there are some things we can look into to reduce this.
The first thing we can do is look into relocating your speaker to help decrease bass. By moving the system away from a wall or corner, or placing the system on or near soft surfaces, decreases bass response. The system's tone characteristics change depending on location and environment.
If this persists, we can also reboot your system to ensure there are no processing errors in the product. This will clear all product settings and return your product to its original out-of-box state.
Finally, you may be able to adjust the EQ settings by your source device. It may be worth attempting to connect your speaker to multiple devices to see if you get a different audio response, this also includes trying different audio sources such as Spotify, MP3, video audio to see if this differs.
If you need any further assistance after trying these steps, please reach out to your local Bose product support team as we will have exhausted all suggested troubleshooting. You can reach out to your local support by clicking this link, selecting your region and scrolling down to Contact Us. Here you will get all the contact information available for your region.