in my opinion the leaves are not getting too much light, and also i don't think there is anything wrong. i think the leaves will gain more color as they grow out.
potentially i am wrong, and this is indicating something, but if anything i would think it would be a nutrition deficiency. however i still say, it's ok.
potentially also, there are some strains that show pink and reddish leaves, variegated. the 'Eureka' lemon is one that has this quality, so if this lemon is related it might be a natural occurance. this is where the pink lemon comes from - a mutation of the 'eureka'. other strains of lemon often have reddish color on the new growth, which
should change to a dark green as the leaves grow.