Syntax definitions and color schemes work exactly the same way as they did in ST2. The only difference is how packages are handled.
and use https://github.com/skuroda/PackageResourceViewer
to extract the files to the right locations. You should be able to use that plugin and just save the file when you are done and it should have the correct name (and folders are automatically created). Remember that you need to do this with both the syntax definition and the color scheme - and a restart won't hurt. You can test if the syntax definition works by inspecting the scope of the tag in question. If it's working as expected, chances are you did something wrong with the color scheme.
As I said in my previous post, I've done exactly this. I used PackageResourceViewer to open the HTML package and to edit HTML.tmLanguage, add the code that I previously posted, which works perfectly in ST2, saved it, restarted, nothing happens. I'm using the exact same color scheme for both ST2 and ST3 which has these new colors defined.
valerij_ wrote:colorcoder does color each html tag in a different color
I want to specifically change just a couple of HTML tags in my scheme. I do not want to apply a rainbow of colors and wholesale changes to my theme (including backgrounds, line numbers, tab indicators, etc.) so it no longer looks even remotely the same.