Questions and postings pertaining to the development of ImageMagick, feature enhancements, and ImageMagick internals. ImageMagick source code and algorithms are discussed here. Usage questions which are too arcane for the normal user list should also be posted here.
colorspace is used to specify internal storage of colors.
type and color profiles is used for external file format storage styles.
The two are closely related when the coder for a specific file format permits but that is not always present. I have no idea of the capabilities of the TGA file format or the coder. This is just general handling.
For more specific TGA info perhaps 'using the source' for the TGA coder, especially the code comments, would prove enlightening.