I have a HP Color LaserJet CP3505n and just replaced the Cyan toner . . . but whenever I print out anyting, there is no blue color on the right hand side. I did buy the toner last year in a package deal (all four colors) but have not needed to replace the Cyan until a few days ago - so, it was sitting in my garage for a year. Do you think that's the problem?

Toner is hydroscopic it absorbs moisture very rapidly. The finer the toner particle is, the more susceptible it is to moisture absorption. It can begin to become a problem when the environment achieves a humidity level of 50% or above. The result can be print defects and/or light printing. For this reason toner needs to be stored in a cool dry storage space.

You need to shake these cartridges before you install them in your printer to evenly distribute the toner. Take the cartridge out and gently shake it from side to side and re install it. Good luck.

I don't like saying call the manufacturer, but in this case....
HP has an "out of the box" warranty when it comes to toners.
If you bought the toner 6 years ago, but took it out of the box 2 weeks ago, your warranty started 2 weeks ago.
Call 1-800-HP-Invent and they will of course want to troubleshoot with you, but it won't cost anything if you explain that you just installed the toner, it's new, and you are having this issue.
They should treat it as "accessory under warranty".
They'll either stumble upon what the defect in their cartridge was, or in all likelyhood they will simply replace it.