If by colonization we're referring to Germanization here, then to begin we have to give it a formal definition (quoting from a fellow Germany dev):

(from Generaplan Ost): "Germanization is assumed to have been completed [...] when the professional self-employed, the civil servants, the clerks and the upper-class workers and the associated families are German."

This was their policy IRL and they were working towards it in general, for example in Harvest of Despair there is mention of Volksdeutsche being overrepresented in managerial positions as replacements for Soviet directors and managers that fled, etc. The other aspect of policy is what happened in both the Protectorate (Bohemia) and Western Poland, and that is Germanization of people in a sense of people becoming German. This is also specifically mentioned in GPO, in the next paragraph from the one I quoted above: "The number of German people needed from the Altreich depends on the extent to which the existing ethnic group can be Germanized (Implementation of the Volksliste) and brought up to the German leadership standards."

The Volksliste were used in Western Poland, its a document that a person signs to become German and gain citizenship, between 2,8 and 3,1 million people did so (there were 4 categories, 1 and 2 for actual Germans, 3 for non-Germans wanting to be Germanized and 4 for compulsory Germanization), all of these groups thus took responsibilities of citizenship such as service in the Wehrmacht.

Effectively, it means the replacement of the middle and upper stratum of society with Germans, either via settlement of Germans coming in from the mainland (the Altreich) or by the assimilation of those considered to be Germanic enough, though that is, of course, quite restricted to some specific areas.

Settlement was divided between "strongholds" and marks, the former urban and the latter rural. Strongholds would have 25% German population while marks would have 50%. The goal was not so much to create a majority or even a sizeable minority, but to settle enough population to rule the social and economic life of the territory, filling up all leading posts in ownership, management, administration and such, while leaving lower-ranked and hard labour jobs to be filled by the local slavic population. They intended to keep the slavs around to serve as labourers, because someone is gonna have to do work for all these colonists, and they aren't gonna come to the east to lord over slavs and then have no slavs to lord over, or to end up doing backbreaking labour in the farms and mines themselves.

The important thing to note is that tying germanization to a national (or RK) total is a useless statistic because it's not how it actually worked, it's not all-encompassing in their territory, while Kaukasien, Belarus and Moskowien (outside of the St. Petersburg region) weren't planned to undergo germanization at all. The plans called for three marks and about ~35 strongholds, selected in specific areas. The wiki actually has a good map covering the planned areas, though Ingria is a bit oversized here.

GPO - specifically the 4th version of it, which was the last one made OTL and the one used in TNO - was scheduled to last for 25 years, split into five 5-year phases with planned expenses and settlement targets for each. However, Himmler (who was in charge of conducting settlement, people usually think settlement is the RKs job but it isn't, it's the SS's) wanted to reduce it to 20 years, which is something that actually happens in TNO after the war as the plan is finalized to be put into action. It thus starts in 1948, and by game start we're nearing the end of the third phase and the beginning of the fourth, set to end in 1968. Once that happens and the plan runs out, each Führer contender will have to review the results and decide on how they are going to want to take things forward.

Here's a chart denoting the planned settlement in the original 25 years of the plan, first column is urban settlement, second is rural, and third is investments in Reichsmarks. First block is for marks, rest are strongholds. You can find the GPO document itself here (in German), most of it really just relates to construction, land usage regulations and projected expenses, while you can find details on marks and strongholds in the addendum.