On 11/25/2015 05:42 PM, Chris Mohler wrote:

I know of no reliable method (aside from having a swatch book and using the mark-one eyeball).  That being said, try this: http://rgb.to/hex/3e479a

Or if you search the web for "HEX to Pantone", you will see some other
tools pop up.

Also, (I think) Pantone used to have a color lookup on their own site.
But I can't find it anymore.

But once again - I doubt any of these tools are super-reliable.  This is from someone who used to mix Pantone ink colors.

Pantone Formula digital swatches are stored in CIE Lab colorspace, which means that it is possible to reliabily choose a close match for a RGB value, given that we know *which* RGB colorspace those values belong to.

An hex RGB value means nothing if we don't know the colorspace, so any conversion will be based on an assumption, we can't really know.

So the very first question is: What RGB is that RGB value? Is sRGB? If not, what colorspace?

Once you know that, you have to convert the RGB value to Lab and find the closest match for your Pantone.
iirc, the Lab values of the Pantone Formula guide could be loaded from Pantone Xref using Swatchbooker.

Gez.