Quoted:
When it comes to the bulk box stuff, the common colors I've experienced were blue for data and white for phone. I hated doing projects at smaller places that used whatever color the electrician had at the time when they installed wall jacks. They'd be blue in one room, orange in another, or a variety, and you couldn't tell if it was data or phone unless it was live and patched in.
The places that needed the most help didn't have the money to fix the problem, otherwise they would've been more organized and done it right.
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Bingo. When contracting an electrician or a datacom firm, specify the material to use. If it's a plenum environment, tell them. If it's a Cat5e network, don't allow for any portion to be of lesser grade, ex: "Cat 5" jacks, patch panels, etc. Specify exactly what you want - like "Superior Essex Cat5e riser cabling in blue, Leviton Cat5e jacks in light almond". Furthermore, insist your circuits are certified. This can quickly reduce variables in what's wrong with your network. Saving a few dollars with the low-ball firm WILL cost more than doing it right the first time.