Hi Cynthia,
You're most likely on the right track. Blu-Ray disks and DVD disks use completely different kinds of lasers when reading the disk; the DVD uses a red laser and the Blu-Ray uses a blue (well, technically violet) laser with a lower frequency allowing for smaller dots and thus more data to be packed into the same space.
So yes, it's entirely possible that your blue laser has failed but the red one is still working. They are almost always mounted on the same head so you may have to replace both at the same time. Start out with some basic troubleshooting as follows.
[[Optical Disc Troubleshooting|Optical Disc Drive (Blu-ray, DVD, CD) Troubleshooting - iFixit|new_window=true]]
Go through some of those suggestions and let us know what you find.