What could help you is the following guide-line. Considering the ff6633 and blue, you chose for complementary colors. When you select ff6633 in e.g. Photoshop, you'll see it has an angle of 15 degrees. As you are looking for complementary colors, add 180 degrees to it and you get 0099cc (rgb + rgb = 255,255,255, in our example 255,102,51 (=ff6633) + 0,153,204 (0099CC) = 255,255,255). Suppose you like this as a basic color, you could pick other blues by changing the B(rightness) value.
It's not mathematics though, it's a guide-line. Maybe you like a blue at 180 or 210 degrees better.
Other options are using contrasting colors (about 90 degrees angle) or colors in about the same range (angle 15 to 30 degrees).
Hope this information was helpful.