When we were selling our house a couple of years ago I read an article about this.

The article said that the color yellow signaled cheerfulness and that you should put yellow flowers outside your house to make it more appealing.

Personally, I like red geraniums with some white nemesia or other little white flowers. Maybe some ivy to cascade over the planter. Some spikes (dracena?) spaced for interest. Easy maintenance, just deadheading. But that's just my opinion, not the "science of real estate"!

I'm putting the link for the article below.

Here is a link that might be useful: tips for selling house

Can't beat geraniums - and you can probably find lots of different colors, from white to pink to red at the big box stores. They combine well with petunias, sweet potato vine (Ipomoea) will cascade over the side, dianthus or "pinks". Marigolds are cheerful and they'll combine well with anything green, white, yellow, blue, or purple. There are an awful lot of annuals to choose from that are easy care and do well in planters in sunny/partially sunny locations. And for a 5' planter, make sure you get enough plants to really fill it in - so the individual plants aren't lined up like soldiers with big gaps in between. Chances are, with annuals for a planter, whatever catches your eye will no doubt appeal to others as well.

I also suggest geraniums. Nice thing about geraniums, too, is you get the impact right away - one or two nice plants is enough to give good effect as opposed to having to wait for the plants to "fill in" like other annuals. Geraniums would do great in the partial-shade planter, not 100% about the full sun in your zone - maybe someone who gardens farther south than I do can chime in and advise you (up here they do fine in full sun)

Nice suggestions above. Geraniums and spikes...that's a combination! I think the salmon and magenta ones have a better pop than the reds, but they all look good. I have a large planter box outside in part sun and the dark blue lobelia can be seen from way down the road, probably because it's such an electric type of blue. Whatever you put it, just maintain it to keep it tidy and alive. There is a house for sale around the corner from me and the guy is asking a half million for it. Nice house but his planters are full of dead topiaries and plants, even at the front entrance! The realtor must be on something to not have picked that one up.

If youy are looking to sell the house this summer....go to a garden center that is getting to close out the summer flowers and buy an assortment of stuff that's on sale....buy lots! Plant it and keep it well watered...if anything dies, pull it out. Your goal is instant pretty not long term garden....go for the glitz! Plant what you can buy ( I agree geraneums are noce but may be gone) and keep it watered and happy selling!
Linda C