Some color combinations.

This is Hague Blue for the interior.

http://pearleandpiercehome.com/2012/03/15/hague-blue-i-love-you/

Go to any paint site (SW or BM) get a color you like and it shows you coordinating colors for exterior.http://www.sherwin-williams.com/homeowners/color/find-and-explore-colors/paint-colors-by-family/SW6230/#/6230/?s=coordinatingColors&p=PS0

If your house is austin limestone clad, then you want to put the blue on your fascia/ eave, window trim (if any - window sashes if the windows are paintable), front door can also go blue or try a bright citrus green -
post a picture so we can advise more. Thinking your hardie board matches the general tone of your limestone - neutral buff. If your home has wood windows or paintable fiberglass windows, then they should go hague blue too. You can do secondary doors / french doors in the hague blue on the exterior. The front door wants to contrast for a contemporary look / modern.

If you have any porch / railing / steps / other house elements / timbers .. . that is where it gets tricky and we need to see the style of your home. If an older home that you are doing with modern colors, consider horizontal fencing / cable rails / other contemporary elements to signal your style intentions. If you have aluminum windows, consider that galvinized tone when selecting other hardware and lighting elements.