All items are colorable. Because of some reflections change the brightness in the paint option to match the separate items that snap together. I have shown the places to snap the items together and once you snap one you will get the hang of it.
It is easier to join the pieces together on the ground and then snap them into place. Build from the bottom (ground) up. Pieces in order are as follows...
1. Down Pipe Base and Grate - Move this into position of where you want the down pipe to grow from. I would suggest for you give some thought to where you want windows/doors and how the end gutter will connect to the end of the roof. This Base item can be moved by the ALT key however it will snap nicely so the gutter should connect to the roof correctly above.
2. Down Pipe Height Extensions 1,2,3,4 - Height 1 is for a Gable Roof with the smallest pitch. The Height Numbers increase as the roof pitch increases and Height 4 is for the Steepest Pitch in Roof. This probably won't be used much unless your Sims live in Austria or Switzerland and it snows frequently.
3. Down Pipe To First Floor and Floor To Floor - These speak for themselves and allows to connect to the level above it seamlessly.
4. Joiners 1,2 - These are the arms that connect the Down Pipe to the Leaf Basket. 1 is for gable Roofs while 2 is for Flat Roofs.
5. Gutter Ends, Gutter Corner and Gutter - Gutter Corner is rotational. There are 2 snap slots so you can have your gutters handle the corners. The Gutter straight piece has 4 slots. I have incorporated 2 inner slots as some roofs aren't a full Sim Square so the roof ends have a neater fit. The outer snap slots are best to arrange of the ground and then when connected transfer to the top of the Leaf Basket.
I have noticed that in some areas the colour of the gutter changes when shadows are cast on them. I have no idea why this happens however I will update in comments should I find a fix for this. It seems to only happen in unusual circumstances involving high roofs.
Enjoy!

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