To show mortar lines on HO I would paint the walls a light grey, then color the bricks with a combination of brown and red colored pencils. This would leave the grey in the mortar area, and give the bricks their color. I have yet to try and see if this works in N but it worked great in HO.
Rather than looking like mortar, this looks more like a brick structure that once painted white. Very seldom is mortar white unless it is made with the sand you see in sand traps on the PGA tour.
Every house in my neighborhood, built in the early 1990s, is brick with tinted mortar, whether for more or less contrast with the brick. Mortar for light colored brick is usually tinted darker, whereas mortar for darker colors is darkened/colored to reduce contrast. It probably wasn't done that way much in the past except on very expensive builds (in the era of many of our brick structures), but today, mortar color is not dependent on the sand color.
The thread refers to DPM kits which are definitely not 1990's architecture. Very little, if any tinting or coloring was done prior to 1970 or possibly 1960. The post war building boom of the late 1940-50's which saw entire communities like Levittown built almost overnight did not offer such luxuries. Most cities and towns were well established with little additional new construction. If one is running steam or 1st generation diesels the tinted mortar on buildings sticks out like a sore thumb.
One other observation. Most brick buildings of late 19th/early 20th Century construction were built with "face" brick on the sides of the of the building facing the street and less expensive [generally lighter color] brick on the sides facing other buildings or alleys. Also, look at photos from those eras, mortar is generally not visible from the distances we use in N scale anyway.
