Review by eric_r_wirsing on allkpop.com.
Their second mini-album has six new tracks, including a cover of "Butterfly" for the 2018 PyeongChang Olympics. [...] This is one of those albums where the rest of the EP is at least as good [as] the title track. Any of these songs could be the one they promote with and I'd be impressed either way. I like the way their voices combine on the harmonies, and Suyeon really shines when she's allowed to. Catchy, and cool and smooth, what else do you need?
"Lucky" is an intro track, with a few vocals. It's fast and fierce, and the chorus is lifted from "La La La."
2. "La La La"
The too short but funky "La La La" is their title track... [Y]ou can't deny these girls have serious pipes.
3. "Iron Boy"
The disco-inspired "Iron Boy" sounds almost like something out of the 80s, and I love the smooth chorus and the way these girls sound together.
"Metronome" is highly representative of what this EP sounds like -- tons of sweet R&B-tinged dance tracks. That synth line is gold on this tune.
5. "Color Me"
"Color Me" is really where they shine vocally. They [...] have sweet voices all over this tune and some explosive parts for the vocals.
"Butterfly" is their homage to the PyeongChang Olympics and a pre-release digital single. It's a cover of a tune from Take Off, a 2009 movie about the Olympics. It's a soft, pretty tune, not to mention anthemic. They lend their trademark sweetness to the song, and Suyeon's vocal pyrotechnics during the chorus gave me chills.