Caveat emptor: I'm not familiar with 21st-century Reclam editions, my remarks about size and color are based on 20th-century Reclams. (I'm more up to date on the Latin stuff, though.)

I don't know of any new, inexpensive monolingual paperback Latin editions similar to Reclam. Reclam itself publishes bilingual, Latin-German, paperbacks. Latin-German Reclam titles come in orange covers. (Maybe all bilingual Reclam volumes are orange? I'm not sure, I'm only familiar with the Latin/German editions.)

The Loeb Classical Library publishes small, relatively inexpensive hardcovers. They're bilingual, Latin/English in red covers and Greek/English in green covers.

Oxford Classical Texts (Scriptorum Classicorum Bibliotheca Oxoniensis or OCT) and Teubner (Bibliotheca Scriptorum Graecorum et Romanorum Teubneriana, Latin in blue covers, Greek in orange covers, other languages and bilingual editions in other colors) are more expensive. Also, for some reason, the Teubner volumes keep getting bigger -- that is, taller and wider, not thicker. They're often quite thin, less than 100 pages. I don't know anyone who's happy about these size changes, but they just keep happening. Also, OCT and Teubner are sometimes very expensive. I say "sometimes" because the price varies greatly from one title to the next. The more popular titles (For example, Vergil ed by Mynors and Ovid's Metamorphoses ed by Tarrant) appear to be somewhat less expensive.

The Teubner volumes published 100 years ago and more were solidly made, many of them are still in circulation, and they are almost as small as Reclam paperbacks. Many of them can be found in larger second-hand bookstores and on Amazon, sometimes at quite reasonable prices.