I have one in my garage in black, 1965 (want to buy Olli? :laugh

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You might want to recheck post 20 as I pasted over a duplicate post with another answer.
As for the Marder II colour, I would be wary of reading too much into B&W photos. It could be a lot of dust. At the time the early Marder II were first produced the standard colour was anthracite grey or Panzergrau, but many vehicles were produced in the much lighter African schemes (various light greenish greys and light browns) for NA service but were sent to the Eastern Front instead. The slightly greenish yellow that became the ETO standard base colour only started to be applied about the time the last of the Pz II D/E were converted to Marder II.
A Pz II D/E chassis could have started as a Pz II D/E, be converted to a Pz II (Flamm) and finally end up as a Marder II, SdKfz 132.
The Pz II D/E were intended to be a cavalry tank for the Light (Leichte) Divisions. These divisions only had a tank battalion, motorised cavalry regiment(s) and motor cycle units amounting to 4/5 battalions and an artillery regiment, less than half the armour strength of a Panzer Division, but about the same in infantry. The 1st to 3rd Light Divisions with Pz II, Pz IV and Pz 35(t), Pz 38(t) and Pz 38(t), respectively, tanks became the 6th to 8th Panzer Divisions after Poland with additional armour and infantry units. The 4th Light also became the 9th Panzer but without much additional armour. If I remember correctly, it was the only one that made much use of the Pz II D/E, the others using the various Czech tanks. Post France its armour was replaced by better kit and the strengthening completed. Chas posted counter art for a Pz II D which is supposed to be one of the PiF counters.