How to make ombre recolors for maxis / alpha hair:
1). CAS - Create standalone recolor, find the hair that you need*, Shift-click on one swatch to select all, click Next, name it.
*if you want to recolor someone else's custom content, you need to put the package into C:\Users\-----\Documents\Sims 4 Studio\Mods first, then close s4s, then open it again. You need to filter content by Custom to find it;2). Press Shift Ctrl C to open the console, type studio.exportall in it, press Ok. This will create a folder in the same location as the package with all textures and blend files;
3). Open the first blend file (LOD 0 ). Select any meshgroup (s4studio_mesh_), switch to orthographic (NUM5) front(NUM1) view, then press NUM. to focus on that selected meshgroup;
4). There are 3 meshgroups in the outliner: the base shape and two hat chops. Click on the eye icon next to each to find the one that is the base shape, hide hat chops;
5). With the base shape selected, switch to the Texture paint mode. In the Texture tab, click on the free slot, you'll see the NEW button appear, click on it. Then click on another New button, change the name, height, press Ok. Then in the Slot tab choose the new texture;
6). Switch to Tools tab, choose Draw brush, enable Use gradient. Brush - Image paint tool - Fill;
7). Click on the <-> button to flip colors so that the white comes first. Optionally you can click on + button to create another color, grey, it will smooth the transition;
8). Click between where the ends are and drag up, close to the hairline, you'll get the same gradient as in the pic;
9). Now, textures generally have margins ( the offset texture around the uv islands). You can dictate how big that margin is in Options tab (Called Bleed), but Blender creates it very oddly for texture painting results. So instead i suggest you to do it a bit differently. Switch to the Edit mode, in UV editor click on the + button and create a new image, the same as before. In Render tab unfold Bake panel, choose Texture, change Margin to 7, uncheck Clear. Image - Save as;
10). In Photoshop open the ombre image you exported from Blender. You'll see that the hairline was also baked, (not sure what determines what is being baked because sometimes it is only the selection, other times everything regardless), anyway, just delete it from the image. Press Ctrl A to select everything, press Ctrl C to copy;
11). So there's this cool trick in Photoshop but it only works with the non-portable version. Open Photoshop, File - Scripts - Load files into stack. Then you can choose all images in the folder s4s exported (beside Shadow, Specular and Normal, they come first) and Photoshop will load all of them in the same psd file! But if you have the portable version like me, open the first image, press Ctrl A to select everything, File - Place, choose the second hair color in the list, place it. Select everything again and repeat until you have all colors in the file;
12). Anyway, there in your color textures file add Solid color fill layer. Alt-click on the mask that was added, fill everything with black. Select everything with Ctrl A, Edit - Paste special - Paste in place. Click back on the layer thumbnail. Then change the blending mode of the color fill. Usually, modes like Multiply, Screen, Overlay, Soft light, Hard light, are useful. You may need to adjust the color to a brighter/darker/more saturated version to get the result that you want.
13). There are other ways. Hide the color fill layer, Ctrl click on its mask layer, add Hue/Saturation/Selective color/Color balance/Layers/etc.
I think Hue/Saturation works best for making ombre hair. You do not need to change the blending mode.
14). Anyway, so you found the right color for blonde, Save as - choose png - Overwrite the corresponding file that was exported from s4s. Do this for all of them, finding the right shade;
15). IMPORTANT: DELETE ALL BLEND FILES, NORMAL,SHADOW,SPECULAR MAPS FROM THE FOLDER. Then open the Standalone recolor package, open the console again, type studio.importall, wait, save.
As for what colors to choose, you can watch videos on color theory but i think it'd be easier to just google "blonde ombre idea" and so on or use maxis ombre hairstyles as a reference.
