Setting Up a Process subject for Visitor ID Card, Vendors ID Cards?

In my company, we have the employee id cards the color of the lanyard is black and the same color lanyard is used for all vendors,visitors, contractors so we could know the difference who is employee who is vendor.
So i request some one to clearly explain me the pros and cons of having same color lanyard or tag across the companies for all 3 different types of entries - Employees, Vendors and Visitors. Please Request to help me in this regards.

dear friend,
employee, vendor and visitor :
Employee : have the photo affixed, use bar code to access, working hours etc.,(Company Logo Should be there)
Vendor : No Company Logo, give this with photo affixed, specify the vendor with his prime supply, gove specific id nos. Else,
Visitor : This card can be used of dual purpose as vendor/visitor - mention the name authorise the security guard with specific id no (have 5o cards serially numbered) give each card to each person either visitor/vendor and collect on leaving the company, get their licence or any other proof till their stay in the organisation, this is essential as this will make the vendor/visitor again approaching the security personnel.
Two Card is enough with different colours
best of luck ....