I mix my baby's lugaw with kalabasa and she's liking it. But when I mix it with other veggies like papaya or sayote, my baby doesn't really like it. Do you observe this on your babies also?

Yes, because even babies have their own taste preference. Persistence is the key! My wife observed that our baby doesn't like carrots at all but what she did is she just continued giving it to our baby, then eventually she learned how to eat it. Another trick would be making your veggies more palatable by mixing a bit of sweet fruits. Eventually you can take out the fruit and he/she will be familiarized with the taste of veggie he/she used to hate and just get over it. :D