Hello!
Here are a few - those are contemporary, not from the 1940's - but they should give you a better idea about the colours:
A bunch of trees - if you take a good look I think you can make out an old tank obstacle (dragon teeth) here. The vincinity of Vistula river doesn't have a lot of forests:
A good example of road typical for the '40s - please note the willow trees:
This one is about May:
Here's one if you want grass:
Here's a good one for August, when the harvest is already done - it must have looked the sami in the '40s - maybe it could be even more typical if the house was made out of wood:
In summer the plants tend to turn yellow:
OK - let me take a break now :-) - tell me what you think and have a nice day
Paweł