OTO is the only yellow chlorine indicator in common use -- that's what you've got, and there is no 'more distinct version'.
The image below gives you approximate colors over a wider range:
Your other option is the K2006 (@ Amazon) kit we recommend. It is a back-titration from pink to clear. I haven't heard of anyone having trouble seeing it, since it's a presence/absence determination. It's also FAR more accurate, when testing chlorine and CYA, then test strips.
And . . . before you waste your money, there is NO electronic chlorine meter that (a) works and (b) costs less than $1,000. And before you consider it (I don't know your budget), you do NOT want the $1,000 version: it takes special handling and regular re-calibration!
Oh, and one more thing. Do NOT confuse the K2006 with the K2005 . . . which might be available locally. The chlorine test in the K2005 is not a titration, but a color-match to PINK shades that many find hard to discriminate.
Bookmarks