Normally mercedes (as well as manufacturers of stereo units)tend to use ISO-plugs which makes it easy to change the head units in vehicles whatever the brand may be.
There are several possibilities for the cable color codes, since mercedes figured it necessary to change these colors throughout the years and models...
brown colored cables behind the radio are ground
blue/white cable goes to the electrical antenna (to be connected to the outgoing (switched) power from the stereo unit)
green/white goes to "GES" which has something to do with the rpm's and speed of the car and is used in some Beckers (Spezial & Exquisit). Not to be used for a Clarion.
red/gray/blue ("93) or gray/blue ("95) goes to the dash lights. This one is to be connected to the illumination of the radio.
black/blue ("93) or pink/green ("95) are powered as soon as the ignition key is turned into position 1 or 2.
black/yellow/green ("93) or red/bleu ("95) are permanent powered.
front left + green
front left - green/brown
front right + orange
front right - orange/brown
rear left + pink
rear left - brown/pink
rear right + white
rear right - white/brown
It is very well possible that the colors at the back of your radio are different from the mentioned colors, but the average Clarion only needs permanent power, power switched by ignition key, ground to function properly. Furthermore you have the possibility to connect an auto-antenna or amplifier to the stereo unit, connect separately to the illumination & connect to a car phone for auto-mute.
After powering the radio it should be possible to determine which cable leads to which speaker.... The speaker cable with a brown line is - and the other (usually same colored cable) is +.
I hope this will help you a little...
greetingz & good luck
with a minor 600+k