You can use the option searchHighlight = TRUE to enable search result highlighting. This feature was introduced in this DataTables blog post. The implementation there did not consider the possibility of searching individual columns, and we have enhanced this feature in DT. Here are some examples:

mtcars2 = head(mtcars[, 1:5], 20)
mtcars2$model = rownames(mtcars2)
rownames(mtcars2) = NULL
options(DT.options = list(pageLength = 5))
# global search
datatable(mtcars2, options = list(searchHighlight = TRUE, search = list(search = 'da')))
# individual column filters
datatable(mtcars2, options = list(searchHighlight = TRUE), filter = 'top')

Note highlighting is only applied to character columns when you use individual column filters. For example, in the above table, highlighting only works when you type in the search box of the model column; for other columns, highlighting does not make much sense since searching is performed via sliders. However, highlighting for global searching is applied to the whole table (e.g. type 21 in the global search box).