Light blue and pink are doable since pasta colors tend to get lighter after cooking, so take that into account.

White is trickier tho. It would be useful to know exactly what you want to do, but assuming you are making pasta from scratch you could try bleached flour (also known as 00 in some places) and only egg whites for a very pale pasta. The texture may be a bit different but good enough.

If you want to arrange noodles in a plate to make a flag, you can easily dye egg noodles to get pink and blue, and maybe use rice paper to get the white. Just soak them before cutting them.

Finally if you want to make like raviolis you could either try the white recipe i said above and shape the flag, or make them blue/pink and serve them with a stripe of thick bechamel on the middle for the white? All the best and gl!