They look very healthy to me!

Josh

With epiphytic orchids, green, white, yellowish roots are generally all good. As long as the root after watering is firm when gently squeezed between two fingers, it is fine. The ones to worry about are brown/black roots that are "squishy" -- ones like that need to be removed as they are dead.

Time for repotting depends. If the media is in crappy condition or it is not a media that works in your conditions, then repot ASAP. Otherwise, it is best not to repot until you see new root growth indicating the beginning of a growth cycle. Orchids repotted at such a time seem to suffer little to no set back in growth whereas repotting when new growth is not under way sometime leads to "sulking". Under the conditions indicated by your photo, it is a moot point.

Usually repotting does indeed involve the use of fresh media though there are exceptions.

Thanks guys! I wasn't sure about yellow roots. I bought some orchids mix but will wait awhile since it is doing so well. What about fertilizer? Should I use it while in bloom and doing good or should I use it when not in bloom?...

Again, that depends -- on both the fertilizer, your regimen, and the type of orchid.

Generally speaking:
Many folks will fertilize with a balanced orchid fertilizer "weakly weekly" -- ie. very weak fertilizer solution with every watering (whether the plant is in bloom or not). Others find it more convenient to fertilize with a little stronger solution every other watering (using the non-fertilizer waterings to help rinse out any mineral buildup). Still others rarely fertilize and so when they do may use a still slightly stronger solution.

Typically, orchids enter some sort of a "dormant" stage after blooming. It may be a very strict somewhat shocking dormancy as with orchids like Catesetums that drop all their leaves and want to go and stay completely dry throughout their dormancy period. Or it can simply be more of a "pause to catch its breath" situation during which the plant still likes its usual conditions but simply does not grow -- neither leaves, nor roots, nor flowers. Instead the plant uses this time to regain its strength. This is common for many orchids like Phalanopsis. (Now it should also be noted that there are some hybrids -- especially among the phals -- that are so highly hybridized that they never enter into any sort of rest period.)

During this pause, fertilizer is unnecessary and is a waste of fertilizer. However if one is sticking to a "weakly weekly" regimen, there's no great loss $-wise as very little fertilizer is being put in the water anyway.