Eyebrows have two sets of textures and alphas - one set is for toddler through adult, the other set is for elders, so they'll have grey eyebrows. I usually make the elder set the same as adults - I do that with hair recolours too, as I like to pretend my sims have hair dye in my little universe, but you can make them white or grey if you prefer grey elders.
There are several ways to make brand new eyebrows... Here's how I do it:
1. Find a photo of an eyebrow shape I like on a real person. Light skin, dark brow colour is best for this.
2. Open the photo in Photoshop. Desaturate it (make it black and white), and then up the contrast and play with the levels/brightness until the skin is completely white, and the eyebrow is still plenty detailed, but the hairs are fully black. Colour over any bits that aren't pure white around the eyebrow.
3. Open an existing face skin texture, to use for positioning the brow correctly. Copy-paste the manipulated black and white brow texture as a new layer in the face texture document, set it to a multiply layer type (so you can see exactly how it's going to lay without the white around it in the way) and scale/stretch/etc. to move the manipulated brow texture into place over the eye in a generally brow-ish position.
4. Duplicate the layer, mirror the copy horizontally, and move it into place over the other eye.
5. Combine the two layers, and invert them, so they've got a black background and white brows.
6. Put a new layer behind the brow layer - fill the whole thing with black.
7. Save what you currently have, white brows on black background, as your alpha for your brow project.
8. Then open your texture for the brows and, well, honestly, I just bucket fill (the ONLY time I use bucket fill, because you really can't tell) with whatever colours I want the brow to be. Black for black, dark brown for brown, pale yellow for blonde, etc., and save over original texture with your bucket fill. If you want normal-coloured elders, save over the elder as well - otherwise desaturate your bucket fill, lighten it a little, and save that for your elders.
You can also just use a bucket fill for the texture and then just play with painting bits of white over a black alpha to make your own eyebrows without using a photo, but I find the more complex set of steps given above gives a much better, more realistic result.
my simblr (sometimes nsfw)
“Dude, suckin’ at something is the first step to being sorta good at something.”
Panquecas, panquecas e mais panquecas.