In Irish "oráiste" is only the name of the fruit, not the colour. "Buí" is the Irish for the colour orange. As I'm sure you realise, "buí" also means "yellow", in fact Irish speakers divide up the spectrum of visible light differently to English speakers (the seven colours of the rainbow are actually a cultural interpretation and have no basis in physics), so in Irish the word "buí" covers the whole range from yellow through to orange. If you want to be more specific about a particular hue, you can use "flannbhuí". This is a bit like using terms like "navy blue" or "sky blue" in English. As well as Peachey's example of terms for "red", another instance of colours not corresponding in the two languages is "glas", which can be translated as "blue", "green" or "grey", depending on the context.

"oráiste" actually is both the color and the fruit (oráiste [sg], oráistí [pl]). Flannbuí is the yellowish color you sometimes see on the Irish tricolor flag in the place of the orange we're used to. It's just a very specific kind of orange-yellow/Pluto-the-dog color. :)

I got curious too, so I did a little research. :) http://miseciara.wordpress.com/2013/08/20/oraiste-v-flannbhui/ I guess that flannbhuí (blood-yellow) is only the colour, and oráiste is obviously the fruit. Hoping a better speaker would tell us if oráiste can also be used for the colour.

I am listening to Raidio na Gaeltachta as I am writing this and they are talking about an weather alert "flannbhuí" for most of Ireland today.

Wrong! My grandmother spoke both Irish and Scottish gaelic. She told me that Oráiste is both the noun and the adjective. Then I found this!!e