It‘a possible it may have been red from the beginning but they were seemingly green when they were still indoors, now I have them outdoors for a couple weeks and that’s when it turned red. Either ways, this has never happened before in the past years I had this tree and just hoping it’s not anything bad.

Exposure to brighter condition is most likely behind this change of color. The color is due to increased production of anthocyanin pigment. It is natures swiss army knife. In this case it is protecting the leaf (really the chlorophyll) from increased photo load. It should revert to green.

Usually the sequence of color change is the opposite. When new leaves come out they are pigmented red/purple to protect the very young leaf from full Sunlight. And then as it matures it becomes fully green.

Yes maybe also paired with cool nights(we still get 40s temps) and sunny days anthocyanins were activated? I also just repotted this too couple of weeks ago if that matters at all.

I am not sure if cold weather is also a contributing factor. Could be in a good way. Too much light and heat could lead to sun burn. May be the cool weather prevented a sun burn.

" It's possible it may have been red from the beginning but they were seemingly green when they were still indoors, now I have them outdoors for a couple weeks and that’s when it turned red. "

I have grown Ichang papeda seedlings inside and did not observe their new leaves to be red. Only the ones outside have red color on the newest leaves. It might have something to do with cold or ultraviolet light exposure.

Something is definitely wrong.. redness isn’t going away and some of the new growth have brown on them and yellow speckles. Any ideas on what’s wrong? This all happened after I repotted my yuzu

I don't know for sure what the problem is, but I would guess the young leaves were exposed to cold too early while they were growing, and did not handle the temperature change well from inside to outside growing conditions.

Also, it's hard to see from the picture, but your tree might benefit from a larger container with more root space. That soil might not be the best. Any way to add dark fertile rich soil or compost in there?

Yuzu is a pretty resilient variety, and can handle or survive more problems than many others.

That’s what I was thinking too.. I bought them indoors yesterday. I actually repotted into a pot 2-3 sizes up from the previous one. I used the 5-1-1 mix as everyone here suggested years ago. It’s so well draining that it keeps the roots healthy

Let me clarify that Yuzu leaves can be surprisingly tolerant to cold (more than other standard citrus varieties) but when we're talking about transfer from warm indoor growing conditions to outside, it's a different story. The leaves won't be tolerant unless they have already been acclimated.

I'm one of the rare people here who have done enough experiments with this to have some idea what I'm talking about.