What looks better weathering tracks?

[pmrossetti]

black ties weathered with brown?
brown ties weathered with black?

 

[Rotorranch]

Whatever looks best to you.

Rotor

 

[zoegraf]

black ties weathered with brown?
brown ties weathered with black?

It depends on the look you want.

I usually go by a prototype photo of the track/area I want to model.

Either way that you mentioned would look prototypical. Brown ties weathered in black could represent a branchline during the steam era or older ties weathered by a frequent coal run. Black ties could represent new ties that have brown dirt on them or simply oil soaked ties in a steam service area.

I suggest you try to get some colour photos of the area you are modelling.

 

[diburning]

Or, brown ties weathered with black = diesel engine leaking oil

 

[Selector]

Black is not a realistic colour for creosote-impregnated ties. They are more like a molasses colour. So, if you want newly-laid newly-impregnated ties, they would look like they had molasses slathered over them...that means shiny. If you want that shiny look, or just for the ties to have the partially shiny look to make it seem like they have been in place for about a year or two, then add a tiny amount of gloss medium to "Burnt Umber" mixed with some black acrylic craft paint.

If you want them to look weathered, then you need to add some grey to Burnt Umber. Note that ties will look best if they vary somewhat. You may want to mix two or three batches of 'weathered tie' paint and alternate strings of ties using one colour or more.

For a branch line or industrial spur, you would want mostly greys, and you would probably want the ballast to be rusty from wash-down from the rails.