Greetings Orange stains in a diaper are usually urate crystals from highly concentrated urine. While common during the first few days of life, this finding is unexpected at 37 days old. This discoloration often indicates mild dehydration or that the baby is not getting enough milk. Kindly visit a pediatrician to evaluate the infant to check their weight gain and overall hydration. Closely monitor the baby to ensure they are producing at least six heavy wet diapers a day.

Keep watch,  orange urine could indicate concentrated urine which in turn may be due to inadequate feeding that leads to mild to moderate dehydration,  keep watch on baby's activity, feeding pattern and urine output.. but best to consult further based on weight and quanitified feed volume as baby is too young

A single orange or pink tinged stain in a wet diaper usually comes from concentrated urine, something urate crystals cause, and it normally settles once feeding picks up. At 37 days this is a bit later than when it's most common, but it's not alarming on its own, especially since you only moved fully to breastfeeding three days ago and he's still settling into the new pattern.