Any colour works on any material; its weave or knit stays. The rainbow keeps the material's own colours.
Add images or text, then drag them on the pattern. Lines show the garment's pieces.
Fitted mesh reshapes to your shape sliders in Second Life, like mesh bodies do (recommended). Standard size is fixed to the size you pick.
Snug sits the fabric just off the skin: mesh bodies are slimmer than the default avatar.
Second Life's own shape sliders. The garment is fitted to the shape you pick here, so download it in the size you wear.
Upload in SL: Build → Upload → Model, tick Include skin weights, leave Include joint positions off. The download includes step-by-step instructions.
Avatar body files © Linden Research, LGPL-2.1, from the Second Life viewer. See notice.