A multi-colored stainless steel necklace with an 18" adjustable chain would feature a mix of vibrant or subtle hues, depending on the specific finish or anodization of the stainless steel. The stainless steel may showcase shades like gold, rose gold, silver, blue, or rainbow tones, offering a striking contrast or harmonious blend. The adjustable feature allows for versatility in wear, accommodating different necklines. The overall look would be modern and stylish, with the multi-colored stainless steel providing a contemporary twist on classic jewelry design.