hmmm... fly fishing is about matching the hatch. It's not as much about colour as it is about pattern and size. The absolute best way to figure things out is walk down to the river's edge, shake the bushes and see what flies out. Or get a small strainer, scoop up some of the dirt at the edge and sift it.
For trout, a good standby is a #16 or 18 Elk Hair Caddis. The Grand is the largest Caddis hatch in North America I think, and the cycle goes on for pretty much the whole summer. Caddis patterns of various sizes and colour will be effective in the Upper Credit and Humber also. Flies are seasonal, so it pays off to know the cycles. You could be fishing topwater with dry flies and all the action is below the surface with nymphs or emerger patterns, and all you'll get is exercise casting. I always have a few beadheads and scuds in my box. Here's a link to a hatch chart:
http://www.grandrivertroutfitters.com/hatchchartwhite.html
The main thing is don't get discouraged. See it as a challenge, and keep trying different things. I do a lot of reading, and I'm still learning all the time.
For bass, pretty much anything that moves and looks like food will work, from colourful poppers to mosquitos. Key there is to find them and be there when they're hungry - then hang on. I've had bass dance all around me on their tail, it's great fun!