Hi there,
On a blue background, won't be a problem at all ... As what we do is reverse the blue in the logo to white, but because we have an additional Teal colour, the logo still holds; #47 and #49.
With regards to the numerals option ... did you mean Roman Numerals?? My only concern with that is, they do have a zero, and the closest options would be 10 (X), 11 (X1), 100 (C), 101 (CI) and 1000 (M) ... all of which don't really say digital, and I'm worried it might confuse people??
Cheers
Angus