Multiple values for single url parameter

[Imaster]

Hello,

I am looking at allowing only certain url parameters via Google Webmaster Tools > Url Parameters.

Basically, I want to allow a few chosen multiple values of a single parameter and block any other.

Allowed: (Single Color)

colors=blue
colors=black
colors=silver

Disallow: (Multiple Colors Combination)

colors=blue-black
colors=black-silver-gold

To set these parameters via GWT, I will have to add the parameter along with its different values separated by comma. I will have to use the following setting "Only URLs with value".

So assuming that I want to allow only 50 single colors type urls, I will have to add them comma separated. Is that ok and fine? So something like colour = red,blue,green

I have also handled it via canonical tags in the page head, but I also want to handle it via the URL Parameters in GWT.

[lucy24]

Before you go any further:

What happens if a random passing human (or an overly inquisitive robot) requests one of those multi-color-hyphenated forms? Is this hypothetical, or does it actually happen on a regular basis?