In the beginning there was - The Microphone…
While microphones can be colored, often deliberately so, there are also many which are not. For example, many omni microphones are essentially flat from 20Hz to 20kHz. They are commonly used in classical recording.
The “colored” microphones are deliberately voiced for a particular sound. For example, vocal microphones are typically highly colored to flatter the voice and to increase intelligibility. Similarly, there are other favored microphones for instruments recorded for pop and rock tracks.
Notice, for example, when Alison Krauss performs live she uses a large diaphragm cardioid microphone for her voice (a Shure KSM32) and a Shure SM81 (small diaphragm cardioid) for her violin. The SM81 is essentially ruler flat. The KSM32 is flat but for a 3dB peak at 7kHz. (Small and large diaphragm also sound different, even if both are exactly the same in frequency response.)
Mic pre-amps also come in various flavors. Some are completely flat with huge bandwidth. Others are colored to provide a preferred sound. Some also have variable input impedance to match or color a given microphone, etc.
It all depends on whether you want to capture the actual sound or create sound for a particular purpose.