Don't be fooled by color alone, many females have outstanding color. Although the rostrum is never developed in females, young males don't have much development either. This complicates sexing younger animals. These are all females.
As cloverthechameleon said: female older than a month old. You shouldn't buy pardalis that young unless you know the breeder and are prepared to deal with a neonate.
Pretty old article, but interesting. I've found im injection to be very stressful to already sick chameleons. I can rationalize one initial injection but not a repeated regime. I wonder if this affected their results? When ever possible oral application should be preferred.
All 3 from the same clutch.
Pic 1 has a nice blue body and yellow head coming in.
Pic 2 Love the blue tipped rostrum and red coming in on his head.
Pic 3 Red dorsal crest.