The 0.65V is forward biased, and depends somewhat on the current. This indicates that it's a silicon diode, not a Schottky (it would be more like .35V in that case) or germanium (even lower I believe). The 40V is with the polarity reversed, I assume? That is probably because the leakage current is increased when it's close to reverse breakdown, which increases the voltage over the resistor.
My guess is that Signal Diode Mk. 1 (which is almost what 1N4148/1N914 means) is pretty close, as long as they're not zener (you would see a much sharper knee at reverse breakdown), Schottky or power. They might be faster or slower, but as long as neither speed nor high current are critical, they're probably fine. I tend to throw these away, since the 1N4148 is really cheap, and I dislike working with unknown parts without datasheets.
The color might be an internal marking or selection by the company that used them, they may have been selected for eg. forward voltage or reverse leakage, or may be different parts altogether.