You need to create a UV map first for the parts not having any decorations.

Thanks, Scrubs. I think I'm getting it figured out. 😃

hI i know this post is old but i need to say how to change a 2 colors piece to other colors for example 12893 mini wig no 45 ,in blender for sure

http://vignette3.wikia.nocookie.net/lego/images/e/ec/PicBCF868FBF775DF3BC1DF99157FD6D2AA.jpg/revision/latest?cb=20130402221055
For example this minifig

Oh, changing the colors of a two-color piece? That's very easy, but it's easier to not do it in Blender. Using the bald spot piece as an example, you would export the model then navigate to the decorations folder. You see an image that looks like this.

http://i.imgur.com/6EaFY75.png

Then just using Paint or any image editor, change the colors. If you wanted to make it yellow, you would change the peach to yellow.

Oh great thanks a lot

Any tutorial of this?

Hi guys, sorry to re-open this thread, but I need more details. Can you @LukeSkywalker please elaborate on your first post? You wrote that you would use any torso with a print and then change the maps/decoration PNG before importing to Blender, but could not use this for parts that don't have a decoration.

Does this apply to pieces that have decorated variants but not in the desired colour? For example, the 1x4 brick has plenty decorated variants, https://brickset.com/parts/6188640/brick-1x4-no-9 among them, but doesn't have any decorated variant in sand yellow colour and the decorated pieces cannot be recoloured in Mecabricks (either that or I haven't figured out how to).

Does this mean I have to use blank sand yellow 1x4 brick and add an UV map to it in Blender?

You are right, you can't change color of decorated parts in mecabricks!

I'm not an Blender expert but i think that if you want to use an existing decoration you can't just change the color of the part in blender because decorations in mecabricks are not made with transparent backgrounds, you'll have to edit the background of the decoration image, or make your own decoration and replace it.

I'll leave it to the experts to comment if i'm right or wrong... 😉

@ViralWinter, I think if there are no decorated parts for the color you need, you will have to either:
-Using any of the decorations, edit the png to what you need in the color you need, and then change the color of the brick itself in Blender
-or add a UV map to a part without any decorations in Blender

I would guess the first one would be easier, but I haven't used Blender in a while.

@LukeSkywalker Yeah, I tried to recolor the part in Blender and the png in Ps, but it always resulted in failure. The brick and the area of the png with changed color both always ended up black in render and my very limited knowledge of Blender prevent me from coming up with the correct way to do this.

I'll probably end up adding the prints in Ps in post...