Several handy resources for creators.
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Color actions have become popular in the Simming community because they provide a quasi-standard to allow creators to color match their downloads.
Popular sets of color actions are listed below.
Once upon a time, Greg Bennett shared a grid with colored squares and rows of letters which is quite handy for seeing how textures are mapped onto a mesh and where they're mirrored or stretched. This grid plus the extracted UVMap should help you easily solve most texture/mesh alignment problems.
For Clothing Textures
Photoshop plugins for Texture Making
Although the Dividers font is no longer available, many floral fonts work very well. You can use multiple rows to make lace fabrics for robes, undies, stockings, etc.
How I Add Details - Jeans
How I Make Texures
Both from Ohbehave's Junk Trunk.
Aquilegia's Linen Texture
For Hair Retextures
Nymphy's curly textures
For Make Up
Neder's Facial UV Maps
HugeLunatic's Default Makeup Packages
For Tattoos and Overlays
Overlay Boxes: What They Are And How To Use Them
For Walls and Floors
ZeroDark's Wood Wall "Blanks"
Goat's Wood Textures (GoS Advent 2012)
[Goat's Wood Texture] at Goat's Attic
Object Templates to Clone
Recoloring and Cloning Templates
Default Replacement Templates
Dinnerware Default Replacements
Custom NPCs Templates