It is not going through a phase. Juniper is evergreen and should always be the deep green you described. I expect that this one is not dying, but dead. Juniper dies in slow motion from the inside out. By the time it is all brown like yours, it is usually past saving. Sorry to be the bearer of bad tidings.
It wasn't entirely clear: "I normally set it out on the balcony" sounds like this is a process--you keep setting it out on the balcony, implying that in between it comes inside. Junipers should not come inside (except very briefly for display). They die indoors, from a combination of not enough humidity, not enough light, and no winter cold dormancy. And being moved in and out is very hard on trees. Normally when you move any plant from in to out, you do it gradually giving it a chance to adapt to the new circumstances.
It may well also have been overwatered. Are the little pebbles in the photo glued on? If so they should have been removed immediately. They are just there to keep the potting mix from falling out when the tree is being shipped. They cut down on air and water circulation, and make it more difficult to know whether your soil is dry or moist (so when to water). With the rocks there, I can't tell what the underlying soil is like. Juniper bonsai are often sold in regular potting mix, but this is very bad for them. They need something much less organic, more mineral and free draining.
If you decide to replace your little juniper, come and do some reading here first....