Today the Arch of Titus appears colorless, but how did this monument look in ancient Rome?As usual, this article is behind the subscription wall. But you can get a good idea of its contents from this brief BHD essay. Aside from the yellow of the menorah, the coloring is educated guesswork.
Using technology, an international team of scholars has digitally restored a panel from the Arch of Titus to its original color—offering us a glimpse of what ancient Rome looked like. Steven Fine of Yeshiva University, Peter J. Schertz of the Virginia Museum of Fine Arts and Donald H. Sanders of the Institute for the Visualization of History detail their restoration efforts in the article “True Colors: Digital Reconstruction Restores Original Brilliance to the Arch of Titus,” published in the May/June 2017 issue of Biblical Archaeology Review.
There have been many, many past PaleoJudaica posts on the Arch of Titus. This one noted the announcement of the discovery of the yellow pigment back in 2012. I have posted some of my own photos of the Arch of Titus here. Some other recent posts are collected here and here, and follow the links. You can find more by running "Arch of Titus" through the blog search engine.