It depends on what you're after or what the track needs. 
I usually prefer transparent eq's for mastering & use color type eq's  for tracking. Sometimes a track won't need much eq at all, sometime color eq's mask or ruin a good track.
Sometimes a track needs 'radical' eq'ing.

There are most definitely both types of EQ, one with colour and the other that is transparent. Both have their uses on individual tracks and busses and in mastering situations. Neither one is correct or wrong, they are both relevant and very important.

The danger with using an EQ that is going to add colour in a mastering situation is you may choose the wrong colour for the music involved. Easy to do and does require a lot of skill to match correctly. If in doubt choose a transparent EQ instead. Transparent EQ's in a mastering situation are perfect when you only want to make a tiny change to an otherwise great mix and leave the rest of the mix totally alone. Something on a transparent EQ can do well.

Great example of an EQ with colour is the Nomad Pultec EQ which I bought recently and used in mastering a Hip hop album. It added some serious sound but the right sound. Client is in raptures over it. Nice transparent EQ is the LP64 which I use all the time on mixes I just don't want to add anything too other than some nice gentle EQ here and there. Mix integrity basically stays the same.

Haven't found it yet - so I have an excuse to keep buying new ones. ;)

The closest I know, for my personal taste, would be McDSP's Filter Bank, but unfortunately it isn't available as a VST. I'm hoping they will see the light and port them someday. They make incredible plug-ins. Not too sure about the GUI though.

Another favorite is the very inexpensive Midnight EQ, from the Focusrite Midnight Bundle ($50 for the EQ alone would be a bargain). 

Most of the time, however, I'll just use the default EQ in any DAW I'm using. I used to dig Sonitus, even way before they were a part of Sonar. Studio One has my favorite bundled EQ (I'd love to see them sell it independently - I think they did before S1 came out), followed by Logic. Pro Tools' isn't bad either.

Pro-Q - I don't know what it is about this one. Intellectually, I get that it's a great plug-in, but for some reason, it eludes me.

Waves H-EQ - same thing. In theory, this one should be my favorite EQ. It has all I want.
112 db's Red EQ should be right next. 

But for some reason, I just don't get it. 

I purchased the FabFilter Total Bundle. I fell in love with Pro-Q's Mid/Side implementation, analyzer and user interface.
Also Pro-L limiter became my new favorite in few days.

Yup, they are not hard to love.  They are FAB!

it would be cool if HarBal could be used as a plug.

i really like WAVES LINEAR PHASE EQ.

is it best?

i don't know, sounds the best to me, of everything else i've tried...


as far as EQ's with a SOUND, i love the Waves Rennaisance EQ for that....
it definitely colors the sound, and happens to be my 2nd favorite eq.

i use the Sonitus EQ for general eq quite often, and it does the job for broad strokes.

If an equalizer added harmonic distortion to my sound, I'd consider it a product defect and probably not use it. Distortion and equalization are, IMO, two separate concepts.