There is no such color mode. You can create two spot colors for your O and V and add them in the Appearance panel to an object with CMYK fill as two additional fills with the desired mixing opacity. Then save the appearance as a style swatch.
Pantone had Hexvector & Hex wrench. You may want to contact them to ask what is going on with their product line, if thsoe even exist. Pantone is notorius for bad support and development/support of their products.
call Pantone at (888) PANTONE or(201) 935-5500.You can also send an e-mail to:email@example.com,or visit our Web site:www.hexachrome.pantone.com