Brand new silver power cord is bright sounding

The silver in the cable is exposing a deficiency somewhere else in your music chain.

IMO, silver may be slightly quicker or give the system more transparency (which is a good thing). It typically should be an addition which increases your systems sense of pace, rhythm and timing and increases perceived resolution.

Sometimes this can be confused with increasing levels of "brightness/sibilance.

I think, it depends on the position from the moon
---> sometimes my silver Power cords give me sonically a touch of orange
earthing, mixed with some purple colored sound staging and a dark
background.
Sometimes I also have a touch of green details with superior blue top End,
linked with a invisible airy medium Frequency area.
I think, the Furutech connectors add that kind of sensitive darkness which helps
me to enjoy the music without wearing sunglasses.
Highly recommended.

Robertsong,
Is this a pure silver cable or is it silver'plated' over copper? Either way you may just need more hours of use.I find the good silver cables to be open,transparent and provide natural tonality.Silver is not inherently 'bright'but it is honest IMO.There are copper cables that can sound bright also, depends on which particular cable and in what system.

Silver is quick and known for helping to deliver as much detail as possible. Your experience is not unique. Silver often leads to a sharpening of the sound. However as was said the better conductance of the silver may be exposing some other weakness in you system. Silver does burn in like all cables and will mellow but only very slightly. It may not be a good match for you. I use Silver on sources both PCs and ICs and then use really good copper down the chain to balance the character of the two metals, works great.