I'm in an almost entirely similar place with number synaesthesia: absolutely no positional awareness for them, and colours for each digit. If I visualise a longer number I visualise the digits as being different colours.

Interestingly, I have the same colours as you for 1, 2 and 3, then:

4 - green 5 - pink 6 - light blue 7 - gold 8 - dark green 9 - dark orange 0 - grey/colourless.

Unlike you, all my colour associations are equally strong, and very usefully, even digits are cold colours, and odd digits warm colours.

I also have colour associations for some but not all letters (but English isn't my first language), and some but not all music notes. I suspect that these associations arose partly from the number colours, but I have no idea why "w" is the same green as "8", and "f" the colour for 5 and not 4.