Are you just trying to get the indigo color or are you wanting to actually do indigo dyeing?
Excuse my ignorance, but could you explain to me what the difference is?
The actual indigo (either real indigo or pre-reduced synthetic indigo) dyes from companies like Dharma, Jacquard, or Yamato are going to be much better options when it comes to actual indigo dyeing.
I'll probably lean towards these over Rit and I'll also try posting over in that subreddit as well.
For reference, this is what I was originally looking at:
