ColorCombine

ColorCombine[{image1,image2,…}] creates a multichannel image by combining the sequence of channels in the imagei.

ColorCombine[{image1,image2,…},colorspace] combines images that represent the color components specified by colorspace.

Examples

Combine RGB channels:

ColorCombine[{redChannel, greenChannel, blueChannel}, "RGB"]

Create an image from separate color channels:

r = Image[RandomReal[1, {100, 100}]];
g = Image[RandomReal[1, {100, 100}]];
b = Image[RandomReal[1, {100, 100}]];
ColorCombine[{r, g, b}]

Please visit the official Wolfram Language Reference for more details.