I've never seen yellow HT leads, but if you really wanted them, you can just put yellow covers over the top, have a look on e-bay there's often engine bay 'tart up' kits. Thats probably the closest you will get
I had some twenty years ago, bought as individual wires from Halfords, think they were called 'Hotwires'.
Can get for MX-5s but are made specially for them.
Just wondered.