You should definitely test our website (http://foodcombo.com) to understand the concept of our project.
Stay simple and flat if possible (not "too much" design or colors).
The "+" (plus sign) should ideally be part of the logo as we intend to use it a lot with our branding and marketing. The + sign needs to look distinctive, a little curvy maybe. It should NOT look like a "cross" if possible (shouldn't be confused with the red cross/blue cross sign or the catholic cross).
Alternative: Instead of a "+" (plus sign), you could also propose another concept related to "combos", like one of the "O" split in two or the two "OO" (of food) as entwined rings. You could even try to represent a visual example of a "food combo" (ex.: a fruit that's half-apple/half-pear, etc.). Don't hesitate to be creative.
But no matter what ("+" or other), it would be great that that part could be distinctive enough to be recognizable by itself (without the word "foodcombo").
The main colors we currently use on our website are: #323232 (mine shaft) and #e75a4a (carmine pink).
For the font, we tend to like slightly curvy fonts that look like it's been written by hand (like on a chalkboard in a restaurant), but you are welcome to propose anything that could fit within our current website design.
ps. Please feel free to share the website with your friends or to send us comments about our project.