Help for a Reproduction of Irish Immigrants outfit

[Rena]

I imagine local plants would be used to dye the material and some colour shades would differ from that of other countries.

https://www.libraryireland.com/SocialHistoryAncientIreland/III-XXII-3.php

[aghadowey]

- Where would they get their clothes, were they mostly manufactured at home ? bought from second hand?

There would have been places in towns to purchase clothing but in the countryside men and woman would have worked from home as tailors and seamstresses.
Years ago we took a pile of old quilts to be recorded for a project by Ulster folk Museum outside Belfast and the expert asked if there were any tailors in our family. She was able to tell us that several of the quilts were patchwork scraps from woolens used in mens suits & was able to date most of the materials with a decade or so. The neighbours across from us were tailors so we suspect that's where the scraps originated from.
It's a bit later than famine era but in the 1901 census you can see occupations-
http://census.nationalarchives.ie/