Hello,
I think, that info what you are looking for, are here:
http://trade.coa.gov.tw/eng_web/product_dm.jsp?user_id=tasc
from this page:
"The lemon grown in Taiwan is the Eureka variety (green rind lemon), it is more fragrant than the [yellow rind lemon] sold in the market and taste better."
btw.: many citrus varieties are green, when ripen in tropical areas
- this is for example, why Valencia oranges from Cuba are not popular for international market - they stay green when fully ripen, and it is not looking good in shop.