How to tell if the bulbs are good

I bought a used double MH retrofit with 2x 175w MH. When you turn the ballast on, the light come on right away, then after about a minute, they start turning blue. No flickering or anything. Are these bulbs still good?

 

bump

 

Bulbs usually start yellow and then turn bluer as they warm up. I have no way to tell if the output is strong without a PAR meter, or at least knowing how old they are/how much they were used and what specific of MH Bulb your talking about.

 

+1 on above

Im using 14k Lamp which is ony a couple of months old
they start faint, build up to a yellowish colour and then by about 10 minutes or so, seemed to have reached full potential in terms of brightness and colour

 

thanks guys. i will change them just to be sure