Typically, you can paint silver on the body where the clear lens will go on.
Then using clear orange/clear red/etc to paint the back of the clear lens.
When gluing clear parts, you can either use a special glue that are design to joint the clear parts (anti-fogging and dries clear) or I just use Tamiya's acrylic clear as an adhesive; it is tacky enough to hold light parts in place. That way you won't see gluing mess...
