Taeyeon | Hyoyeon
Up and down ogami ajjilhage
You and me dalkomhi dagawaseo
What you want nal milgo danggiji
I’ll bring you back in
Up and down jakkuman hesgallige
You and me daheul deut dahji anha
What you want nareul maemdoneun aemaehan you and me
eoreuni doen neowa naega sijakhaneun nori
hemaeljido molla aju heungmiroun magic
ajjilhajiman kkeuteun al su eopsneun geim
Oh oh oh oh oh oh oh oh
du nunboda ppareun nae son ane deun ge mwonji
han baljjak deo dagawaseo majchwo bwabwa eodi
hanabuteo yeolkkaji da jongil
Oh oh oh oh oh oh oh oh
aemaemohohan sarang ttawin no no no no no
geunde eoneusae ppajyeodeureo oh my god nega mipji anha
Huh maeil nan aega taji uh wae nega joheun geoni
Oh oh heeonal suga eopsji I’ll bring you back in
Up and down ogami ajjilhage
You and me dalkomhi dagawaseo
What you want nal milgo danggiji
I’ll bring you back in
Up and down jakkuman hesgallige
You and me daheul deut dahji anha
What you want nareul maemdoneun aemaehan you and me
Ooh ring ring ring ring ttaeron budeureopge
Ooh ring ring ring ring ttaeron sikeuhage
jangnanseureoun repatorin no no no no no
jeomjeom deo gipi ppajyeodeureo oh my god naega michyeossna bwa
Huh maeil nan aega taji uh wae nega joheun geoni
Oh oh heeonal suga eopsji I’ll bring you back in
Up and down ogami ajjilhage
You and me dalkomhi dagawaseo
What you want nal milgo danggiji
I’ll bring you back in
Up and down jakkuman hesgallige
You and me daheul deut dahji anha
What you want nareul maemdoneun aemaehan you and me
ijeneun malhae jwo jeongmal nal saranghandamyeon oh oh oh
jogeumman soljikhi jom deo wa jwo deo gakkai~ bring you back in
Huh jinsimi daeche mwoni uh ne mami gunggeumhaji
Oh oh neoui ipsure damgin ooh jinsilgwa geojit
Up and down ogami ajjilhage
You and me dalkomhi dagawaseo
What you want nal milgo danggiji
I’ll bring you back in
Up and down jakkuman hesgallige
You and me daheul deut dahji anha
What you want nareul maemdoneun aemaehan you and me
Color Coded Heaven 
These lines are deffinitely Hyoyeon besides the rap part, i recognize her voice, also an article about Taeyeon featuring Hyoyeon in the album mentiones them going back and forth in the chorus
Huh maeil nan aega taji uh wae nega joheun geoni
Oh oh heeonal suga eopsji I’ll bring you back in
Up and down Hyoyeon-> ogami ajjilhage
You and me Hyoyeon-> dalkomhi dagawaseo
What you want nal milgo danggiji
Hyoyeon-> I’ll bring you back in
Up and down Hyoyeon-> jakkuman hesgallige
You and me Hyoyeon-> daheul deut dahji anha
What you want nareul maemdoneun aemaehan you and me
ijeneun malhae jwo jeongmal nal saranghandamyeon oh oh oh
jogeumman soljikhi jom deo wa jwo deo gakkai~ Hyoyeon-> bring you back in
Hyoyeon-> Huh jinsimi daeche mwoni uh ne mami gunggeumhaji
Hyoyeon-> Oh oh neoui ipsure damgin Taeyeon-> ooh Hyoyeon-> jinsilgwa geojit