From Auctung Panzer website:
This should help you out as for colors used. Panzer Grey was used on panzer IV as well as Tigers. There are many variables to GE paint schemes.
Also, you should do a search for decals or reference for panzer models. You might be able to find some stuff there. Please note that these are not current RAL color standards. Some shades are close, but there was a different time ral color standard during the war.
On August 19th of 1944, OKH ordered that dark yellow (RAL 7028) was to be factory applied as the base colour with dark olive green (RAL 6003) and red brown (RAL 8017) for use in camouflage patterns. In addition, to those three main colours, small yellow, light grey or white spots were applied on green and brown areas, while small green spots were applied on dark yellow areas. This overall camouflage scheme was known as the "ambush" scheme so common on late war Panther and Tiger II tanks. As with any other scheme there were numerous variations depending on the unit, its location and supplies available. On October 31st of 1944, OKH ordered that dark yellow (RAL 7028) was to be replaced by primer red oxide (RAL 8012) as a base colour with dark yellow (RAL 7028) or field grey and red brown (RAL 8017). On November 31st of 1944, OKH ordered another new colour scheme to be introduced. Dark olive green (RAL 6003) was the base colour with dark yellow (RAL 7028) and red brown (also known as dark chocolate brown) (RAL 8017). Sometimes red brown (RAL 8017) was replaced with "brick" red brown (dark red) (RAL 8012) colour. Similar case was with dark green (RAL 6002) and dark olive green (RAL 6003). Also due to overall shortages, many vehicles were only painted in overall base dark yellow (RAL 7028). In early 1945, dark yellow (RAL 7028) was again to be used as the base colour with red brown (also known as dark chocolate brown) (RAL 8017) and dark olive green (RAL 6003). All schemes introduced from October 31st to the last days of war, were hard edged factory applied colour schemes with disruptive edges defined sometimes in white (RAL 9002). The use of washable white winter camouflage paint was widespread on the Eastern Front but rare on the Western Front. In the spring of 1945, new scheme was to be introduced with dark (panzer) grey (RAL 7021) as the base colour with red brown (also known as dark chocolate brown) (RAL 8017) and dark olive green (RAL 6003). It is unknown if it was ever implemented due to the overall state of the German Army. The colour schemes introduced in 1944 and early 1945, were applied in variety of patterns and often colours were not exactly the same as specified. Different colours were a result of use substitute paints and ex-Czechoslovakian army paints (e.g. dark green, cream and dark brown). The choice of colours and patterns depended on local and weather conditions as well low level unit orders that reflected where and when particular units operated. In addition, foliage and mud were often used for more convincing camouflage or to make up for paint shortages. It is also reported that late in the war interiors were painted dark yellow (RAL 7028) instead of light cream or ivory colour (RAL 1001) due to shortages and need for armoured vehicles
also, try this link for some ideas. You'll have to scale the colors from whats on this page.
http://bsdi.usppp.com/wwiiscalemodels/schemes/panzertarnung.html
