It kind of depends. I'm not sure what the red babies out of red lines look like or if it varies a lot. I've had red partridge hatch and they were partridge looking with a nice red tint as chicks. Then I've got the mille split boy and my red frizzle girl. The frizzle was from a red father and a red penciled mother. Both she and the mille split boy were very light yellow/white as chicks but with some black markings (like a few black dots/stripes running down the back). I think the wheaten based reds like that can tend to look really light downed as chicks sometimes.
These are the one I think were eb (partridge based). The male is kind of red partridge + some other genes that spread the red into other places like the chest etc. The female equivalent looks more classic partridge but more red.
As chicks
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Male
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Female
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And then the little mille split which seems to be wheaten based looked like this as a chick. The little red frizzle girl (who I don't have a picture of handy) looked really similar but with fewer black stripes. The smooth satin girl in the picture also has dominant white involved so pretty much looked like a yellow chick.
Mille split boy as a chick
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Mille split a little older (I think a lot of the time the red comes through more vibrantly in boys which I suspect this one is)
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Red frizzle satin and red smooth satin girls
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Oh congratulations! What a pretty little one too!
I'm still not sure. I would have said cockerel if the little one wasn't from your flock just for the comb. The crest and tail has me leaning slightly more towards a boy but I'd still wait on this little one just in case. I see the green sheen in my black pullets sometimes too so I wouldn't pay much mind to it.