Making rubber spikes

I have a commissioned prop with spikes that could potentially injure user and spectators if they're made from wood or resin.

I thought I could make them out of silicone or urethane rubber but it looks like neither will take any paint (they need to be silver and gold). Smooth-on does have some color pigments but they don't come in metallics.

Any suggestions to this problem?

I used to make all sorts of rubber spikes from simple faux police spike strips to full on boarding pikes for bad guys and pirates. Dont ask this out loud, but, whats the size and shape of your spike? Soft or hard, rubber (lol, again, not out loud). Rubber will hold paint fairly well if its sprayed on in a light dusting and NOT a heavy coat. Youd be surprised how many props you see on camera are rubber and painted with krylon. Another trick is to use metallic powder over the part after painting but while the paint is a little tacky. That locks the powder in and it can be buffed.

here is an example form the knife I did for Tom Hollands 5 or Die, thats the rubber knife which was indistinguishable from the metal one.

Wow! That looks amazing! Is that urethane?

My spikes range from small 1/2" L x 1/4" d to 3" L x 3/8" d.

urethane it is and you should have no problems making those sized spikes in rubber. Just make sure you use a dusting of baby powder in the mold and brush out any air bubbles when pouring in the rubber. Its not like a resin pour, you will have to actually brush the rubber in the mold or use a curved (not sharp) edged item to dislodge any air pockets between the mold and the rubber.