One way, of course, is just edit the color of your 3d entities. If they are tied to your drafting technique, just copy the info to "3d layers" and change them there. We always use red for new wall lines, but that doesn't make a nice looking model. I usually copy info to "3d_Wall", "3d_Roof", etc. and edit colors to make my model look nice.
It's really simple, but first, look at the color palette. Under Tools/ Color palettes you can click on any color and pick "edit" to bring up an edit box that lets you change red to anything else. That only affects the way you see it on screen. But, if you want red lines in 2d and something else in o2c you need another option.
What you really need is under View/ Rendering Settings. In the top left corner, pick the color radio button, and pick red in the color box either by using the left / right arrows or just click on the color box to bring up the current color palette and pick "red" for your color to work with. Below that is "Rendered Color". You can click on it and pick any other color from the palette, or edit any color in the palette to make it just right.
The "Rendered Color" is what is used when o2c develops the model.
You can also adjust diffusion and ambient factors (I rarely do), reflection and highlight (makes shiny cars look nice), and opacity (make any glass in light cyan look like glass. You'll also want to pick matte or glossy for paving, metal roofs, etc.
"Self-illuminate" works nice for ceilings when you go inside your model, so it looks bright instead of shaded from the sun inside. Always check "render backface" because various construction techniques sometimes leave a triangle (elements are always rendered in triangles because triangles are inherently flat) facing the wrong way and will appear "missing" if you don't render backface.
"Smoothing" is tricky. You can make an 8 sided column look like a smooth cylinder with lots fewer triangles (less math) than a 360 sided column. On the other hand, there are times when faces meet at reduced angles that will be shaded strangely.
The best deal is "Texture". If you check that one, you can browse to any image (look under DataCAD/Texture for a bunch of them) and make your red wall look like brick or anything else. You'll have to trial and error the scale to make it look right, but o2c typically looks pretty nice with default settings.
In the upper right corner is a block, sphere, cylinder, or teapot to show what your color/texture will look like on display (really handy if you do lots of teapots).
"Background" lets you pick any color for the background of the model, or you can chose to use an image, handy if your project is being added to a site you have a photo of. The image will be stationary, just manipulate the model util the scale and perspective matches what you need.
