Hikari has good quality and the larvae are bright red. I've been told that if they are brown its likely that the pack has been defrosted or partially defrosted at some point. I don't see this with Hikari but I don't know if they add something to keep it red.
The one thing I don't like about Hikari is that there tends to be less food per bubble than other brands I've tried, and the larvae are smaller. Just today someone (on another forum..shh!) was saying that he thinks they put more water in it. He was saying its a better idea to get the flat packs because of this and the fact that they are less likely to defrost. Check around the edges of the pack to see if they are brown, and don't buy if they are, he says. Sounded like good advice to me.