Just taken delivery of a new to me Norco Search. Its very much a black and red colour scheme as below but i'm going to put my preferred saddle on it, the saddle is white. The red bar tape is a bit faded so needs changing anyway.
So white to match the saddle or black or some colour combo black with white?

Black version of your favourite saddle and black bar tape. There is no other way!
The white saddle is going to look a bit odd (though only when you're not sat on it). But white tape is going to look wierd too. I'd go with white/red or white/red/black tape to help tie it all together.
Something like this
https://www.wiggle.co.uk/deda-loop-bartape

Black saddle and black tape - sorry. Whilst coloured saddles/tape looks good, ten minutes later it looks tatty. Just got some Profile Design DriVe tape - very nice and grippy, and the best finishing strip I've ever used. Black of course.
My white saddle is a specialized toupe carbon, they dont make them any more. It was an ebay bargain and cost me about £40, would cost about £200+ for something similar in a colour of my choice.
Black, or something jazzy that's red/black. The colored tape always looks pretty manky.
Giant Stratus?

Similar coloured bike to me.
I had this...

Then went for this when I changed bars...

The tape in the second pic also comes in a black/white fade white might look decent with your white saddle. It was around £10 on eBay.
Brazen it out and go for red again.
Did that on my road bike (was black as stock) and it's better for it IMO.
Harlequin mixing of red and white tapes. But it might get grubby quickly.
@Scotroutes that Deda Loop tape looks nice enough but £35 for bar tape is a new low (well, new high) 😀
If it's going anywhere near off-road don't put white tape on it, unless you have a workshop roll and like taping bars every few weeks.
Deda Presa is ace and comes in a few different highlight colours, including one with red highlights
I'd paint the bike.
Black
Yellow, with a black saddle, then insist on riding into a headwind, through pissing rain and up any farm track you can find while pretending you're Belgian.
My bike came with a white saddle and white tape, I think I initially replaced the tape with white again but soon realised it just gets dirty looking way too soon. I only use black now
@uwe-r I have a white Spesh Toupe I'm no longer using. Would it be of any use to you?
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Black.
That is pretty much the saddle I have although mine has no red on it - its just white with Toupe in an off white. Its just a bit jarring with everything else being red / black / grey.
I have 2x bar tape colours on order:

and this one:

I'm going to give the grey a go first.
@scotroutes is that a 143mm? My Alias just snapped on me.
Or failing that, what did you replace it with and how does it compare?
Edit. Sorry, you've answered that for me before. It's a Specialized Phenom.