Hello gold_finger,
Thank You for your help

I had not tried
Gedit, only Leafpad.
I have installed Gedit and it did have 6 colour schemes by default.
I done some searching and made my own custom colour scheme using
Scribes Theme GeneratorI then followed
this info To modify the built-in themes, copy them from /usr/share/gtksourceview-2.0/styles/ to ~/.local/share/gtksourceview-2.0/styles/ and edit the text files.
First trying to copy the theme file to the first location (3.0 though), it would not allow me to add the xml file into the styles folder, no message occurs just greyed out copy or paste functions, I then tried to move it to the folder it produces a red circle with line across it symbol, and won't move the file.
I then looked for the second folder which does not exist at this path.
I then tried to alter one of the existing templates in Gedit (using Leafpad), with the new theme code, when I opened the program it didn't use the new code , when I rechecked the theme I had altered it had not held the code for the new theme. I removed it and replaced with the copy/backup just in case it made a problem.
I then used the function inside Gedit to add new themes and it loads the new theme correctly whilst it is located in the templates folder. Plus I will save it to a usb flash drive.