Mazal tov on the birth of your baby!
It is difficult to assess a very light pink without seeing it directly. Lighting conditions can also affect assessment. The ideal light for evaluating cloths is daylight, in the shade.
We recommend having this bedikah cloth assessed by a local halachic authority, rather than assuming that it is not valid. If youd like to share your location with us, we can try to make a local referral.
Our page on the postpartum period, here, might also be helpful to you moving forward.
Please let us know if we can be of further assistance.