Parkitect has a few scenery items and textures that are not recolorable. On this page you can find a full guide to all known ingame colors used for these items so you can match your own recolorable items to match these colors! This list contains color codes to match terrain paint as well.
All colors and guides on this page are provided by AstroTron.
Grass Dead Grass Sand
#2E6E27 #535831 #C5AF82
Dirt Soil Snow
#965A34 #402D20 #B1B1B1
Ice Ash Rock
#9BABB8 #121212 #6A6A6A
Grass Dead Grass Sand
#42A038 #81874D #FFE5B3
Dirt Soil Snow
#D5814A #5F422F #FFFFFF
Ice Ash Rock
#D5EBFF #1B1B1B #9D9D9D
Pillar
#89634D