Eh, memang boleh jadi macam tu lepas tukar formula balik, biasanya ambil few days sampai a week untuk baby's tummy adjust. Warna greenish-brownish atau yellowish-tan macam tu actually normal during transition, lagi-lagi kalau sebelum ni dia on soya milk. A few of my mum friends anak dia sama je, but kalau najis dia jadi consistently loose lagi, berapa kali sehari ke, atau ada mucus/darah, better check dengan doctor sebab mungkin formula baru ni tak suit je. Monitor aje dulu for a few more days, kalau dah solid dan colour stable, you're good!