I have a lady wanting a cake themed to her home country, She is from Venezuela. I want to make a flag, id like it to look as thought its a big flag draped over half the cake. My question is since this flag is three colors (red,blue,yellow) how would i make it into one square sheet of fondant. Hope im explaining myself clearly. I dont like the idea of painting fondant, it just give a messy look IMO.  

You can roll the three colors, thin them at the edges and attach them to each other with water so they will look seamless but a safer bet, since you're draping it, might be to roll a long base color and attach all three color strips to the top of that base. If it wasn't draped, it wouldn't be an issue! :) I did a bandana on a cowboy cake that was draped, but I used a mix of 50/50 fondant and modeling chocolate because I was worried about draping the red fondant and having it crack.

Thats a great idea, so 50/50 gumpaste/modling Chocolate works well?

I used 50/50 fondant and modeling chocolate for the draping on mine. Not sure how gum paste and modeling chocolate would hold up! ;)

what about making the cake in the shape of the country with the flag colours? I have done Australia and Zimbabwe like that before, and recently I did the Mauritian flag which has four stripes of colour.  Each cake was covered in fondant.  to get the stripes straight was a bit of a pain, but what I did was cut a strip bigger than you need with one straight edge.  place that on the cake and butt a ruler up against it to keep it straight.  then place the next strip of fondant and butt it up against the first.  I cut the bottom edge while it was on the cake using a ruler again to keep it straight.  then do the third strip.  trim around the cake and then add your stars.  Just a suggestion. good luck.