My red swordtail babies are clear when they are born,too. It takes about 3 or 4 weeks before they start getting splotchy red color and eventually they turn red. It's kind of creepy the way they are born,little clear things with huge eyeballs.
I have bright orange platies and they just had babies and thay are almost seethrough!!! So don't worry they will get color! unless they are cross bred with other fish for example when guppies crossbreed with other kind of guppies babies maybe white or albinos!!! but i am sure they didn't crossbreed! just wait and see!!!
My marigold swordtail had fry last month and the first batch (which I could only rescue one!) was a really pale yellow color. Her second batch (again I only found one!) was a darker orange color.
im a molly nut but i have had a swordtail have fry before and they were a clerish collor then they turn to there colors when they get bigger, its no big deal , dont worry