Can anyone advise me on how to achieve this color with SMBC?  

It is most likely created by mixing pink with a touch of blue.  A lot of times I use Wilton's color right system to get create colors and for a bright and bold purple similar to what you have pictured they suggest pink and blue https://www.wilton.com/cms-color-right-coloring-icing-color-chart.html

Grrr, I wasn't done!

Wilton also says to achieve a mulberry color (again I think similar to what you have picture) they say to mix rose with a touch of royal blue (https://www.wilton.com/cms-icing-color-chart.html)

that's showing as a barney the dinosaur purple on my screen -- if I remember correctly, black was needed along with the red & blue to get there but idk there are so many variations of colors now -- black is different than it used to be too -- idk

and in my experience smbc does not hold deep colors like that at all well

could you air brush it?

K8, that's very good to know.  I don't use smbc very often, but wanted to use it for this cake.  I'll experiment with it and see.  May have to use regular bc.  Airbrushing is a definite possibility.  Thanks! 

Freckles, Thank you!  I'll start in the direction of rose with royal blue.  In my mind, that is the direction this color goes.  I need to get that Wilton color right system.  I've heard great things about it and I'm terrible at figuring it out myself.

I think you can still use SMBC for this one - I've used deep colours with SMBC previously and it has been just fine. 

I'd probably be using a mix of colours.... some rose + blue as mentioned above, maybe a little electric purple as well.

I've attached a pic I did recently which was a dark hunter green sort of colour, this one is SMBC. Obviously a totally different colour but you can see how lovely and deep a green it was.

On this same topic and speaking of having to use a lot of color to get the desired deep shade, is there a favorite brand of icing coloring that doesn't give much flavor?  I use the Wilton gel colors but when making buttercream a very dark color, I can "taste" the coloring.  I try to mask it with lemon or orange flavoring but sometimes it's not enough.  Is there a brand that is better with less taste?

Thanks!
Christina

Learn to start with a similar base color   Lik if making red tint your white a pink,yellow, or orange before adding red Americolor is a better brand here in the US   Also make your colors the day before using