\pdfoutput=1 \setbox0=\hbox{\TeX} \directlua0 { callback.register('define_font', function (name,size) if name == 'cmr10-red' then f = font.read_tfm('cmr10',size) f.name = 'cmr10-red' f.type = 'virtual' f.fonts = {{ name = 'cmr10', size = size }} for i,v in pairs(f.characters) do if (string.char(i)):find('[tacohanshartmut]') then v.width = tex.wd[0] v.commands = { {'special','pdf: 0 1 0 rg'}, {'node',tex.box[0] }, {'special','pdf: 0 0 1 rg'}, {'down', 100000}, {'node',tex.box[0] }, {'special','pdf: 0 g'}, } else v.commands = {{'char',i}} end end else f = font.read_tfm(name,size) end return f end ) } \font\myfont = cmr10-red at 12pt \myfont This is a line of text \par \blank \font\myfontx= cmr10 at 12pt \myfontx Here is another line of text \par \bye