Because James Webb Space Telescope observes infrared light, here, a very deep mid-infrared, it is impossible to tell the actual color they would appear. For those appearing quite red, it is likely objects (not planets) are invisible to visible light or even Hubble.

If the image was composed maintaining spectral accuracy and calibration of the different wavelengths assembled to make color, blue would imply that there is more shortwave light flux (the end closer to visible light) than seen in longer wavelengths..

The red giant Betelgeuse, for example, emits most of its light in visible red, not down into deep infrared, so it appears blue in a transposed spectrum.

Very distant galaxies might even appear purple (blue + red) or green, from addition of searing ultraviolet brightness and the dust swirling around young stars, shifted into infrared by the expansion of the universe.